Confirmed
-Mario: Mario Finale
-Donkey Kong: Konga Beat
-Link: Triforce Slash
-Pikachu: Bolt Tackle
-Pit: Palutena's Army
Yoshi: Super Dragon
-Samus: Zero Laser
-Bowser: Giga Bowser Tranformation
-Kirby: Possibly Cook
-Zelda: Maybe the big light beam that she did at the end of OoT
-Peach: Maybe she will summon the star spirits like she did in Paper mario and strike every one with a giant pink beam LOL...or maybe Rage from super princess peach
-Fox: Cover Fire, the same thing you did in Melee in the great fox stage, where you call the Sleepy and Pepi or whatever their names are and will start shooting at your enemies, and they can not hurt you.
-Diddy Kong: He will take out his electric Guitar and stuns everyone around him, they can make it differet from Konga Beat.
-Pokemon Trainer: He will call Ho-Hoh, it works like in Melee but the Fire Tornado will be bigger, powerfuler and will move around the stage, from side to side or something.
-Zero Suit Samus: I dont know lol, maybe she willl gether suit back and do zero laser again but without taking the suit off after it.
-Ike: I dont know anything about himaside from him being the hero in one of the newest fire emblem game.
-Wario: Nucear fart lol, like he did in the trailer.
Unconfirmed
Captain Falcon: He get inside of the Blue Falcon and starts running over everyone from side to side of the screen, you can control the direction of the Blue Falcon by tilting the control stick Up and Down.
JigglyPuff: She will use her Hyper Voice attack, it damages everyone in the stage critically, but doesnt have knockback, it only stuns.
Ness: PK Rockin, lots of beams of different collors will come from different directions, ending with a big colorful wave like explosion around Ness
Luigi: I dont know, maybe using his psychic powers from Mario Strikers Charged
Ganondorf: Ganon Transformation
Ice Climbers: They wil summon a big blizzard that will hit and frezee everyone lol.
others maybe later