Pac-Man.
If he gets in, cool, if he doesn't, meh.
I don't think his chances are as high as most people think they are, though.
Also, totally Mewtwo, and I actually really want it to happen, not really because I'll play as him myself, but because to lose a completely original moveset with no real alternative must have been harsh, and shouldn't ever happen again as far as I'm concerned, plus, I do like him as a Pokémon and everything. I won't really be mad if he's not back, but I can totally see why people want him back so badly, and will be happy if it happens.
K. Rool too, even though I freaking love the DKC games, I don't really care about him too much as a character, but I think he's more than deserving to be in.
Any Fire Emblem character. I want both Ike back and a newcomer, again, will probably not be playing much as either of them (save for Marth, who I find pretty fun, though he's already confirmed and is a no-brainer at this point) but Fire Emblem has gotten pretty big lately, and it'd be cool to see some more representation, even if we end up with three blue-haired men with a cape and a sword.
Takamaru. To be perfectly honest, I have no ****ing clue what's this guy all about and what's up with the sudden popularity he's gotten lately, and he looks extremely bland and uninteresting to me whenever someone posts a picture, but if he really is that popular in Japan, then they should just go for it.