Here is a list of all tricks and skips I have currently found, documented in text and video:

¤¤Note: These tricks need a setup and do not yet contain "specifics" about actions such as where to start a jump or reference geometry on the map to name a few.

¤¤¤Tensuns¤¤¤

Sharks skip: At level start, head towards the left side of the island you begin on. By wiggling between the sharks that block off the end of the level, you can reach it without being eaten, granting access to flight time on top of the ship and the second to last objective, skipping the first objective and all its platforming.

¤¤¤Killer Expo¤¤¤

Faster door trigger: Upon entering the small spaceship at the begining of the level, immediatly fire a star and guide it towards the bottom right. With some precision you can hit the door in the other room, triggering the next part of the level, and exit the small ship immediatly to progress.

Gatekeeper Skip: After triggering the door, immediatly head towards the second to last objective, the missile test center. At the far right of the wall surrounding the missile test center, A guard informs you that the gate is locked at all times. Jump on the Gatekeeper's head, and then jump and try to get a third jump on the wall. If successfull, you may accomplish the second to last objective, skipping three other objectives and granting access to the final objective of the level.

¤¤¤UltimaCrash¤¤¤

Get to boss location right away: On level start, head towards the first objective but do not trigger it. Instead, walk up the path to the top right where the checkpoint is, enter it, and throw yourself off the level. You will respawn with WillFall next to you. Move a few meters farther up the path with the checkpoint, making sure WillFall is following you (He will fall).

Push WillFall towards the edge, right under a path that is just too high to jump on, where you would return from after accomplishing the second to last objective. When he is near enough the edge, jump on WillFall. His small collision box will give you enough height to land on the second to last objective path. Follow that path and touch the flying robot to access the final location.

House Skip: At the final location, the house is locked unless you accomplish an objective. By abusing the weird geometry of the house, you can jump on it and drop down on the other side, which is unlocked. Enter in, and you may fight the boss to trigger the end of the level.

Boss Skip: When the boss apears, lure him towards the big nuclear rocket next to the millenium falcon. When he is near, jump on him. If successful, you will get damaged by the Boss. By holding down the jump button, you get another jump from ontop of the boss, granting you access to the lever completing the level.

¤¤¤Technomummy¤¤¤

Cut the power with WillFall: Jump on WillFall, giving you enough height to blast the power generators of the Iron Museum without having to do all the platforming

Final door skip: The door cutting off the end of the level has a small thin platformunder it. These thin platforms push you ontop of them as soon as your head goes over them. By using jet fuel to fly under the platform right next to the wall with the door, the platform and door will push you into the final area, completing the level.

¤¤¤Earth¤¤¤

The whole level can by skipped by abusing level geometry and jumping over the laser walls sectioning off parts of the level.

Found some skips on N64. Will keep posting them here to this playlist if I find more: https://youtube.com/playlist?list=PLJ6sYdZKbEoy4ddSVoaitLdL9G7etzg9c