They don't have to be Nintendo characters, since Snake is going to be in the game, but they have to be characters that have made an appearance on a Nintendo console, and they have to be characters that have not been confirmed, like Snake.

Konami - Snake Sega - Sonic Capcom - Megaman Ubisoft - Rayman

Sonic the Hedgehog

Sonic, Ryu Hayabusa, Megaman, Protoman, Cloud, and Bruce Campbell

Still no Crash love? I'm insulted...

Crash was pretty cool in his PS1 days, but now he's as bad as Sonic, except with less nostalogy value. I'd love it if they included Ganondorf like he was in the final boss fight of Twilight Princess. A heavy and large swordsman around the size of Bowser and Donkey Kong would definitely be an interesting character. In Melee we only have Roy/Marth and Link/Young Link with swords, and the only confirmed new swordsman Meta Knight appears to be very small and light as well. Ridley would also be extremely awesome. A fast, but relatively light flying character the size of Bowser/DK, possibly with weird ranged weapons? Yes please! I haven't been following Pokemon much, but I hear Lucario is pretty popular at the moment, and as a Fighting/Steel type would be pretty simple to put in Brawl. There is bound to be at least one Pokemon from the Diamond/Pearl generation, and I would prefer if it was one of the less humanoid ones. I know Pikachu and Jigglypuff are not exactly humanoid, but something that isn't bipedal, and doesn't fight with kicks and punches like all the other characters. Pokemon is their chance to include a character that is totally different from all the others, and they've probably realised it. Umm... I got a bunch of other ideas, Melee being my all time favorite game after all, but I'll let you guys have a turn now. =P

I remember reading that ridley would be in it

There was a forum post on a completely random forum some months ago that claim Ice Climbers+G&W+Young Link were out, and Ridley+Young Bowser+Wind Waker Link were in. The guy who started it admited the made the whole thing up within hours, but it had spread so far in so little time that there are still people who believe it. -_-

Sonic, Mega Man, the guy from Shatterhand http://en.wikipedia.org/wiki/Shatterhand or take out the Ice Climbers and add the Double Dragons!

I would love Diddy Kong Dixie Kong King Dedede Rayman Sonic Sarah Kerrigan (I know it is unlikely but I really want her)