King Boo, I don't like the idea of using him.
Axem - Who?
Cel Shaded and Shadow Link - You do NOT need 4 of the same bloody character.
Lanky - Dear god no, not the most retarded Kong. I'm fine with Diddy, but they should have Dixie instead of Lanky. Funky? NEVER BEEN A PLAYABLE CHARACTER, he's had his aeroplanebarrels, garage, airport, fishing game and such, but I don't really want to play as him, OR Swanky.
Slippy and Peppy? No. They don't deserve it, they already have a dang cameo.
Raichu - Dear lord no, we DO NOT NEED A THIRD BLOODY PIKACHU VARIENT!
Blaziken/Hitmonchan/Vigroth - They all seem to have the same fighting style. Choose one, not three.
Those ones need nerfing :p
But, I'd probably add in uh... One of the Tetrisphere block robots. Banjo and Kazooie (Well, they ARE rare owned and Microsoftish now)