I've made a few fan fighters passes in the past, and now I feel like making one with NO LIMITS. Still implementing the game character rule (albeit only because I want to save non-games for a later date), but other than that a character can be as wild, disappointing, unfeasible, obscure, or moveset-potential-less as I want.
Waluigi
Crash
Dingodile
Muddy Mole
Jill and Drill Dozer
Bubsy
Dribble and Spitz
Peppino
Eggman
PaRappa the Rapper
Of these, Dingodile; Bubsy; and Dribble and Spitz are the only ones I wouldn't seriously rally behind. (second rep for series that isn't even in yet, character famous for being in bad games, characters with next to no moveset potential) My desire for Jill, Peppino, and Muddy surpasses rationality so I'll stick by them forever.