Some new, some already known.
Several Assist Trophies have been revealed for the upcoming Super Smash Bros. games on Wii U and 3DS during today's Nintendo Direct. The full list of Assist Trophies, the game or series they are from, and the Smash Bros. version they appeared in, is as follows:
Andross (Star Fox) (Wii U)
Devil (Devil World) (Wii U)
Knuckle Joe (Kirby) (Wii U)
Saki Amamiya (Sin & Punishment) (Wii U)
Lyn (Fire Emblem) (Wii U)
Nintendog (Nintendogs) (Wii U)
Waluigi (Mario) (Wii U)
Dr. Wright (Sim City) (Wii U)
Skull Kid (The Legend of Zelda) (Wii U)
Mother Brain (Metroid) (Wii U)
Midna (The Legend of Zelda) (Wii U)
Ashley (WarioWare) (Wii U)
Dark Samus (Metroid) (Wii U)
Chain Chomp (Mario) (Wii U)
Isabelle (Animal Crossing) (Wii U)
Elec Man (Mega Man) (Wii U)
Color TV-Game 15 (Classic Nintendo JP Only Console) (Wii U)
Samurai Goroh (F-Zero) (3DS)