This is a list of glitches I've found in the game, listed according to their usefulness. There are probably more glitches to be found, and if you do find out a glitch not listed here please let me know and I'll credit you and include it here.
The list within each category is in no particular order.
Useful glitches:
1) Block glitch:
Button presses: BLOCK (hold) + INTERACT (can be mashed)
Done by starting the block stance and then interacting with enemies/objects.
This one results in several glitches. The most useful one is interrupting enemy's actions by triggering their dueling stance. This can also be simply followed up by sword attacks or be followed by dealing damage (HEAVY) or throwing them away (LIGHT). Note that the latter two can be spammed repeatedly by pressing (INTERACT) + (HEAVY)/(LIGHT) quickly, possibly dealing damage more quickly than conventional sword attacks.
Another glitch can be activated by doing it next to an object you can carry: this will activate the red/green arrow, with it gaining more brightness with each (INTERACT) press. This seems only visual and useless speedrunning-wise (it looks cool though).
Finally, if mashing the interact button, the player can cause enemies to either slowly but consistently get past (through) them, or cause them to push the player and get them stuck (such as in the first level, where the crank has to be placed).
It's also possible to reposition the characters by attempting it next to a hatchet/bomb barrel.
2) Infinite Specials/Throw glitch:
Button presses: SPECIAL/THROW + SWITCH CHARACTER (quick)
This glitch is activated by starting a ranged/special attack, then quickly switching to another character, resulting in not using up any ranged weapons. However, because of the way the game works, it seems to be taken as if your partner is performing the attack instead, meaning it'll do less damage.
Since Jack's special causes instant death to normal enemies, it can be used regardless to deal with these quickly. However, Will's special will be very weak, so use it only to hit targets while preserving the hatchets.
3) Bomb height glitch:
Button presses: THROW
This glitch consists in throwing bombs at walls or platforms above you from below. The fire will go up instead of staying at the same height, which allows skipping some detours and allows to deal with several enemies up high from below.
4) Idle Boss glitch:
Not sure as to why it happens, but it's possible to have a boss idle for some time. So far this isn't precisely an exploit (since the conditions to make it happen are yet unknown), although players can actually replay a level (or restart runs) until they get it.
Can happen to at least Pequeno, Barbossa and Alberto Chaves.
In Barbossa's case, you can attack him repeatedly for a long time without him reacting in any way, apparently. This seems like it can happen several times in a row (to him at least).
It seems like it can happen to normal enemies too if getting too far from them (with the best example being The Damsel and the Dead, getting close to the last stone wall without destroying it will usually result in an army of enemies behind being idle)
5) Stomp glitch:
Happens to at least Blacksmoke. When a stomp attack is used, if the player hits a wall during the knockback effect (and flies through/next to the boss?), there's a chance the boss will be hit several times as well, which for Blacksmoke usually ends his smoke phase completely.
6) Early trigger glitch:
So far only found in Trial by Tavern.
It's possible to line up Will's hatchets to destroy the box in which the parrot is from the hallway that leads to the room it's in. This may be achieved by using Jack's special finisher too.
Apparently caused due to walls not having proper collision, as it's possible to gather wooden barrels and boxes close to the wall to the left until they eventually go through it and disappear.
7) Health chest glitch:
By opening a health chest with one character, then quickly swtiching to another and getting the health coin it's possible to heal both characters if both are close enough to the health coin.
8) Clone glitch:
By spamming Will's infinite special + infinite bombs on Tang #2 and her clones, it seems her HP bar will suddenly drop when the clones are defeated (apparently the more clones defeated, the bigger the HP loss). This can make her fight much quicker.
9) Infinite lives glitch:
By simply switching characters right before a character dies, the game will restore ~25% HP to said character without reducing the number of lives. Note that this does NOT restore ranged weapons.
10) Insta-death glitch:
It's possible to insta-kill enemies with bombs even if they shouldn't die to it. It's still unknown what exactly causes it, but the best way to see it is in Formosa Fling by simply throwing a bomb to burn the warriors, and restarting the level until it happens.
11) Insta-throw glitch:
At times by pressing (THROW) quickly, it's possible to throw hatchets/fish/bombs faster than intended.
12) Knockback cancel glitch:
It seems possible to cancel the knockback animation if holding target/lock-on or block when it's supposed to happen (or a bit earlier).
Potentially useful glitches:
1) Clash glitch:
Button presses: LOCK-ON (hold) + INTERACT (mash)
This glitch is activated by targeting an enemy and then clashing swords with him quickly.
The usefulness of this one is rather potential than actual usefulness, but it's possible to quickly move an enemy around the map with it.
However, this seems to vary with each enemy type, even triggering some weird circling movement around the player at times.
2) Enemy ghost glitch:
This glitch consists in an enemy being idle and invincible (at times out of bounds). This enemy doesn't count towards the number of enemies you have to defeat when that's the objective.
This glitch can happen unexpectedly at times, and seems to happen when the player gets too far away from enemies, causing them to idle and perhaps some enemies not being fixed back when the player returns.
3) Death glitch:
As the name implies this glitch is activated by dying, which pushes the player's hitbox slightly forward (I've always held forward when doing this but I'm not sure yet if it's required, as I haven't been able to perform this consistently yet).
This allows the player to clip through overgrowth/webs without destroying them, as well as getting past invisible barriers (but not by getting past them but by getting above them).
It doesn't seem to actually cut time yet.
4) The LOVE glitch:
This happens when Will/Elizabeth say no to violence, give up on piracy, embrace love with open arms and run towards an enemy, hugging them. This can be more easily seen in the last level of the game, after all violent actions the characters committed/plotted in previous levels, seeking greater redemption for such evil acts.
This loving act can soothe the enemy's soul, making them give up on violence, too. For love knows no limits, this can touch even a boss' heart, such as Alberto's, who is secretly a very compassionate man and rescues kittens in his spare time.
5) The Nope glitch:
This is a glitch in which at least Jack says nope to entering Temple Terror during the first cutscene. Was I recording? Nope. Was I smart enough to process it before restarting the run due to timeloss? Nope. Have I ever gotten again? Nope. Do I know what happens? Nope.
6) Barrier break glitch:
It seems like breakable walls/barriers can be broken by unconventional means; usually by enemy attacks, a burnt enemy running amok close to said barrier or a powderkeg. Most of the time this is only visual, but as of now there's one exception: the mandatory breakable wall in Pirates Cursed and Even Worse. This seems like it can be broken by dying in front of it or by...running against it at a certain spot? The timesave seems small though (3-5s tops).
This can happen with the wall blocking access to the map piece within the same level too, but this time it's only visual.
This can also be seen in The Last Shot, in the first room. Enemies can break the rocky wall that the boulder's supposed to break later (in fact, this barrier can be "climbed" using the death glitch, but it seems to trap the player between the boulder and the invisible wall, although oddly enough the player can "climb" the barrier again and return to the first room).
Another one can be seen in Viking Landing: it's possible to break the ice wall at the start of the level with a powderkeg.
7) Object collision glitch:
This glitch consists in objects around the map not having proper collision when intended to, such as stacking up ranged weapons on an intangible barrel (causing the player to go through it and seeming to be knee-deep into the floor).
It's possible to go through the boulder in The Damsel and the Dead when taken down. It is unknown if this is useful at all, though.
A treasure chest in Sacked Without a Shot can be consistently glitched. To do this, the player must open the left chest at the very start of the level, then rescue the woman, then come back, and the chest will be intangible and the player can go through it.
The floor can also have weird collision, making enemies stand on "invisible platforms" (like at the beginning of The Hero of Port Royal). Enemies can also get knee-deep into the floor (like inside the cell (W) at the beginning of "Stop Blowing Holes in my Ship!").
Useless/Miscellaneous/Detrimental glitches:
1) Out of Bounds (OoB):
Can happen by either getting taken down and/or dying, but the principle's always the same: the character's hitbox gets out of the playable map.
However, the player usually spawns in-bounds shortly afterwards, making it (so far) useless for speedruns on a basis.
The only enemy attack to get it so far is the sniper's melee attack, although others probably work, too.
2) Forward roll glitch:
By performing a forward roll, the player can at times get either get stuck in place during the roll animation or move backwards a great distance.
The reason behind it is unknown and so reproducing it may not be consistent.
3) Invisible enemy glitch:
Can happen in "The Bigger the Boat...": at times the Paladins blocking the way (actually an invisible wall, although you can move them around by attacking them/using bombs at them) remain even if you defeat them (with audio effects and all) and they won't really disappear until you've cleared all the enemies onboard.
4) Player collision:
Can be glitchy in some corners, due to the height variable in general behaving weirdly. An example can be seen in the first level by trying to jump over the bridge's corner by using Overhead Slice.
The most notorious one is rolling forward against the corner "hidden" next to the stairs in "Prisoners of the Pearl", after defeating Mallot and the door being open with two pirates coming up. If done in a certain angle the player will go high up and then be locked and descend slowly until the floor is reached.
5) Deloading parts of the level:
It's possible to (seemingly randomly) deload parts of a level as you progress through it (or go back towards the beginning of it). This seems to only last as long as the player doesn't get too far from the transition and doesn't seem to be of any use yet.
6) Rolling glitch: This seems to lock the player and prevent them from moving unless it's done by rolling. The cause seems to be trying to use block right before interacting with something. There's no consistent fix yet.
7) Cannon glitch:
It's possible to make cannons intangible in this game by either getting attacked as you stop using it or using a roll before the cutscene that leads to the cannon minigame (this one leading to the character being only able to move by rolling, as in the rolling glitch, but upon interacting with the cannon both the character and the cannon will move at the same time). This usually renders the cannon useless for the rest of the level, and if activated by using rolls it can end up glitching further, causing the...
8) Fall glitch:
After making a cannon intangible during the cannon minigame, it's possible to go through it by rolling, resulting in the character unable to move or do anything other than blocking (at times stuck in some sort of falling animation instead). If the player tries to switch characters and roll through the cannon as well, it can result in both characters sort of "jumping" around the ocean as the player switches characters and tries to move around. This will last until the cannon minigame is over.
A different variant was found by Mind Pulp: if you stay on the edge of a pit trap, then try to go in as the game attempts to "lock" the area to prevent you from falling into it, it will result in the character being locked in the falling animation and unable to fight apparently. Even if you get a knockback effect during the "lock" process it's possible to remain glitched until the player gets taken down again.
9) Sword glitches:
At times the swords can have some visual glitches, specially after a cutscene. These can be either an invisible sword, a sword being controlled by using the force (unsure if this actually gives extra range) or a fire sword for Jack if his special was used before the cutscene (the fire effect seems to be only a visual effect).
10) Directional controls glitch:
This can happen if the player interacts with a cannon. It seems to involve character switching while the player is using the cannon. When activated, the glitch will change the directional controls of the player so that moving the character around the screen will be confusing (i.e. right will be forward, forward will be left, etc.).
11) Drop Item glitch:
This may happen when an enemy is bound to drop an item upon defeat, but is too close to a boundary. It's easy to notice because the enemy will drop an large quantity of said item instead of just one.
Found only in Dauntless Derring-Do as of now (with one guard giving 4973659324 half bells instead of 1).
12) Red markings glitch:
If the camera gets too close to Jack's face, the player can start seeing textures around his hair as highlighted in bright red. This visual effect seems to disappear if the camera gets further from him.
13) Mallot glitch:
It's possible to have an active Mallot during both the time he's locked in the brig (by attacking him with bombs for example) as well as during the last cutscene (this last one seems to be caused by the characters' positioning right at the end of the 2nd fight).
14) Camera Zoom glitch:
At times the camera may not move with the player and get stuck instead, often resulting in the player moving further and further away from the camera until a cutscene or an event takes place and fixes it.
It can also happen if pushed by enemies into a corner, making the camera get stuck really close to the character (seeing their model insides).
15) Stalagmites glitch:
In Viking Landing, there's a chance of not triggering the first set of stalagmites and the enemies in the area if the player runs in a straight line through the cave (perhaps due to how the trigger was placed). However, this is only visual, as an invisible wall is where the stalagmites are supposed to appear, preventing the player from advancing anyways.
This can be fixed by either walking in a zig-zag of sorts throughout the cave or, if the invisible wall is reached, by walking backwards a bit until the vikings come out.
16) Ghost character glitch:
If you spam interact + switch characters when both of them are close to a cannon, it's possible for both characters to start pushing each other until they both are placed at the same coordinates by the game, making both models go through each other.
17) Enemy lock glitch:
At times an enemy may be locked in place, even if he's running. This does not prevent said enemy from attacking the player, but the enemy will still be unable to move around the area. Seems to be fixed when the player gets away from the enemy.
18) Special spam glitch:
If the player manages to get into a deloaded area, it's possible to use Jack's special (finisher) and quickly switch characters while the other one is into the loaded area. This will result in the finisher being loaded along with the area every time the area is loaded, which means this can be spammed my merely moving the camera around if close to the transition.
This seems to be visual only and last only until the player advances a little and the area gets loaded properly.
19) Warp glitch:
If the player tries to use the specials glitch in certain spots, the special will be cancelled and the character will be warped to a different place (the place where they started the level?).
This can be seen in Broadsides, when attempting to use the specials glitch with Will between both cannons aboard the Interceptor.
20) Ricochet glitch:
At times enemy shots will bounce off surfaces and then adjust their trajectory mid-air to hit a target (but can still miss the player and hit objects instead).
21) Stuck Co-op glitch:
Showcased by Mind Pulp. It seems like at times the game might not let both players get out of certain areas or progress until (apparently) they move around a bit.
Further testing in Co-op would be needed to confirm this, as well as if it's specific to certain areas, if it's easy to fix, etc.
22) Grab glitch:
If the player tries to grab a barrel or a box, but quickly switches characters at the start of the animation, the other character will idle while holding it in place (providing there are no enemies nearby). If the barrel/box is destroyed while the character is in said animation (like by using Will's special), the character will still remain in the same animation despite not carrying anything.
Getting taken down fixes it.
23) Special cancel glitch:
The effect is similar to the warp glitch. By using the special but quickly interacting with a red skull right after starting it, the special's visual effect will begin but everything will be overridden by the interaction animation. If using Will's special, the PotC skull will appear but nothing will happen.
This can be done with normal attacks too, but that seems intended and nothing out of the ordinary seems to happen.
24) Stun glitch:
By simply pressing block right after getting hit, it's possible to make an enemy react as if their attack was blocked despite being hit by it.
25) Character lock glitch:
It's possible to get a character locked in place, unable to do anything, in some places.
Can happen at least in "Where There's Fire, There's Blacksmoke" if a character gets too close to the far end of the ship (between both cannons).
Another way to get it seems to be trying to pick up a powderkeg while being taken down at the same time.
26) Powderkeg glitch:
It's possible to start a light slash while next to a powderkeg, then quickly switch characters before it hits and observe the powderkeg "breaks" without exploding. This is only visual though, since the more or less invisible powderkeg is still in place and functions normally.
27) Invisible NPC glitch:
At least the woman flirting with Will in Trial by Tavern can be invisible or deloaded during the first cutscene.
28) Double Infinite special fail glitch:
By attempting to do the infinite special too fast it's possible to use Will's special twice in a row, with the second special using up all ranged weapons despite switching characters quickly. The reason behind it may be that the special key is pressed too often before switching characters. It's like a mix between the infinite specials glitch and the insta-throw glitch.
