This thread has too many little tricks to let it fade away. I'll add a few more.
We'll call this the nair edition.
1) During Rainbow Cruise's upward transitional period, Snake's Nair and Dair will auto cancel in a single full hop.
2) The height required to do a full nair is Snake's normal jump and about one extra head of height. An example would be on Ps1 during a transition, you can often times jump from the stage to the white lip with an auto canceled Nair.
3) Snake can auto cancel his full hop nair on numerous levels due to tilts on the level, such as Lylat, Halberd, Yoshi's Island, Castle Siege, PS1, Delfino, and so forth.
4) On certain platforms on Delfino that are structured akin to the Brinstar right most platform, you can start a nair in the center, and tilt slightly to the right/left and auto cancel it while still on the same platform.
5) If you drop beneath a platform and then jump immediately, you can do a full nair/dair and auto cancel it on the platform. This enables you to grab a grenade from a shield drop and do a full aerial. You actually have enough time to pull another grenade, fast fall through the platform, and instant throw one grenade, jump, and instant throw the other. Needlessly complicated. =p
6) You can run off the ledge, immediately jump back to the stage while nairing, and auto cancel your landing.
6) Auto Canceling a Nair against an opponent's shield should give you -2 frame advantage. If your opponent attempts to grab, they can be Tilted.