Mega Man: This is the one character I want to appear more than any other. And I'm talking the
original Mega Man; not X, not MegaMan.EXE, and not MegaMan from Legends. The real Mega Man. (To be honest, I expect that if any Mega Man appeared, it'd be EXE or X, since that seems to be where Capcom is putting their money now. Note that I don't exactly hate X or anything, I'd just love to see the original Mega Man return in a game that doesn't make him all chibified.)
If Mega Man were to appear, he'd have to have his trusty chargable Mega Buster, plus maybe some other cool Mega Man items like the Super Adaptor. It also wouldn't be too far-fetched to imagine that, since Mega Man absorbs the abilities of his enemies, he could do the Kirby thing and be able to imitate other fighters (though I imagine it could be done in a Shang Tsung-type way rather than initiating an attack that results in copying his opponent's moves). Alternatively, he could have some of the more iconic weapons from various Robot Masters, such as the Rolling Cutter or the Shadow Blade.
Proto Man: I doubt they'd use two third-party characters from the same series, but if they did, Proto Man would totally have to appear alongside Mega Man. He could use his shield in a variety of ways, and many of his moves would probably be similar to Mega Man's.
Sonic: I'm not a Sonic fan (have barely played any of the games at all, in fact), but I still understand how awesome it would be to finally see the Mario vs Sonic fight happen (though this probably would've been a hell of a lot more relevent about a decade ago).
The Amazon: This will never, ever happen, but c'mon. Pro Wrestling was a badass game and you know it. Since he's from a wrestling game, he'd probably have a lot of grappling moves, which would make him bad for melee battles but effective in close-quarters, one-on-one fights.
Sub-Zero or
Scorpion: Once again, this will never, ever happen. A man can dream, though. Obviously, each would retain his moves from the Mortal Kombat games.
Donkey Kong, Jr.: If for no other reason than to possibly further retcon Rare's confusing DK/Cranky thing. It'd be a lighter character than DK while retaining some of his daddy's power.
Kamek: He might be too minor a character to make an appearance, though I doubt anybody would be upset if he did. Could use some magic/mystic moves.
Pac-Man: He's a legendary video game character.
Zero Clothes Samus: Awright.
And now for a list of characters I hope Nintendo doesn't waste a character slot on:
- Bowser, Jr.
- Baby anybody.
- Waluigi (wouldn't upset me that much, but he really isn't a super-important character).
- More Pokemon characters. Maybe I'm biased because I'm not a Pokemon fan, but Pikachu, Pichu, and Mewtwo sucked in Melee (I haven't played with Jigglypuff too much, and from what I understand she's a real powerhouse if you know how to use her, so no beef there).
- Young Link. To be honest, I kinda liked Young Link in Melee, but he isn't a necessary character. Just consolidate his moves into Link and use that space for a totally new fighter.
- Generic Mario enemy. Nintendo has done this a bit in recent Mario sports games, which is fine in those games because they need to fill a large roster with all Mario characters, but I really don't care to play as a Koopa Troopa or Dry Bones in Brawl. I don't really expect this one to happen too much, but still.