All missions 100%: just like it says complete all missions, however an issue is the repeatable missions. My proposal is that you have to finish those missions at least once.
Olimar low%: rescue olimar with the minimum treasures, onions, flarlics, upgrades, items, missions completed, and materials collected.
Oatchi low%: cure oatchi with the minimum treasures, onions, flarlics, upgrades, items, missions completed, and materials collected.
Daddy%: idea by Dazzreviews2 on YouTube, getting to and defeat the empress bulblax fast as possible.
Pikmin%: get at least one of every pikmin type: reds, yellows, blues, purples, whites, rock, winged, ice, and glow.
Onion%: get at least one of each onion type: red, yellow, blue, purple, white, rock, winged, and ice. Maybe put the purple and white onions in a subcategory.
Extra Hand%: Finish Louie's "Fit for a Feast" quest and acquire the Extra Hand gear.
Solo Pellet%: Slight extension to the above. Recover a pellet without the help of Oatchi or any pikmin.
Sage Leaf Trial: Beat every stage of the Sage Leaf Trial in order.
this game needs a meme category, and cool% is perfect for that
Minimum Pikmin%, a run where you use the minimum amount of pikmin to beat the game.
Low%, a run where you beat the game accomplishing the lease possible. (I do not know the exact number, but it's just trying to save Louie with as few rescues/treasures/caves explored as possible.)
No Onions%: Save Louie without getting any onion (obviusly not counting the red onion).
No Pikmin Discovery%: (I don't even know if this is possible) Save Louie without discovering any pikmin (obviusly not counting red pikmin).
Edit: just discovered that in the No Pikmin Discovery% you can save olimar but not louie because of the two water wraiths that you have to kill in the final cavern.
I'm with Voidwig for getting low% going.
Anyone know how we would start deciding what's worth what? If the % is the same and I've person has a bunch of tiny treasures and the other has an onion for example.
what about a swarm% where you have to rescue the musician and finish his quest to get all the musical treasures? honestly you could do that for all the endgame items, rawrpaws already said extra hand% and solo pellet%, but we can extend that with infinite sprint% and pluckaphone%, and then maybe have one where you have to get all of these items, although honestly im not sure how many people would run them. maybe 1000 pikmin%, where you have to get 1k grown? that could be interesting, cause which would be faster, doing areas and getting new enemies, or just focusing on pellets? might get kinda stale though...
i like the idea of onion% get all the coloured onions, this run have you complete main game up to olimars rescue, complete shipwreck story and complete the sage trials. the run ends the moment you collect the last onion.
if youre interested in more ideas for an extensions board, could add something like "all areas no upgrades" since its possible to 100% all areas without buying anything from russ other than the 2 scorch guards since theyre required to enter frozen inferno, everything else is optional, I did this myself for a challenge run, in the spirit of a challenge run as well, the rules could state that you can only use the scorch guard for entering that cave, then must have it unequipped after entering
Rainbow % = get all the pikmin as fast as possible
So you would have to get red yellow blue purple white winged rock and ice
Not sure if glow pikmin should count since the game doesn't count them as a pikmin at the end of the day when it shows how many pikmin you got/died
The run would end as soon as you get the last pikmin cutscene