Possible Final Smashes
Yoshi- Summons a stampede of Yoshi, or possibly brethe fire like Mario 64 DS
DK- His Bongo Blast attack or his Banana Fairy attack (both from DK 64) or he jumps atop a player and beats them senseless (from Jungle Beat)
Peach- Pshyc Bomb or Sleepy Time (from Mario RPG)
Jigglypuff- Hyper Beam, Self-Destruct (might cause S.D. or 999 %) both are from Pokemon
Pichu- Volt Tackle, Zap Cannon
Mewtwo- Destiny Bond, Future Sight
Luigi- Either an uber thunder attack, Vaccum up his foes, or uses the vaccum to exhaust fire, water, or ice
Falcon- That Super Falcon Punch from the anime (might cause S.D. or 999%)
Fox- Either summons Arwings to attack foes or will make a super combo like Link
Falco- If Fox has one of the above, Falco might have the other
Ness- PSI gaming, Brainshock (might cause button control to randomly alter), Paralysis (cause stunnind duh) or Rockin Omega
Ice Climbers- Summons a blizzard or avalanche
Mr. Game & Watch- Possibly will cause a radom and cartoony events like in the Game & Watch series
Marth- Possibly similar to Link's
Roy- Might use flames and will cause super damage
Young Link- Again, similar to Link's
Zelda- Possibly a typical magical spell that will cause MASSIVE DAMAGE
Sheik- Will either randomly an unlimited supply of needles or knives rapidly leaving the opponent unable to escape
Meta Knight- Summons a super tornado to knock everyone very far
Wario- Possibly make his Wario very strong like in the first trailer
Snake- Will randomly drop random powerful bombs all over the place
There you have it. Sure, I got a bit sloppy at the end though