I've decided to splinter this into a Wii topic and a SSBB one. The speculation's only going to keep heating up. Since all the cool kids are doing it, let's make our own suggestions for characters! A top 5 even! Any character you can think of you'd want to be in Brawl, but try and come up with some reasons why you think they deserve the spot.
5. Cure Black & Cure WhiteSeries: Futari wa Pretty Cure
Creators: Toei Animation

Don't mind me, this is mandatory... Two normal girls chosen by fate to fight the forces of Darkness with the aid of the Power of Light, not only for themselves but the entire universe. They have a cool fighting style with a mix of martial arts and energy attacks and they're popular with all the kiddies! Can you say sales?
Stage Ideas: Garden of Light: Picture it. A gigantic glistening field of hills and flowers... And for traps? The forces of Darkness break the terrain up piece by piece!
4. Ippongi RyuutaSeries: Ossu! Tatakae! Ouendan
Developer: Nintendo/iNiS

C'mon. How badass would it be to beat your friends down with a MALE CHEERLEADER? The guy's got rythm, style, and he's not too bad to look at either. I could even see face cuts being part of some of his skills all hi-ougi-like.
Stage Ideas: Tokyo, Japan: The people of the city along with other Ouendan regulars cheer him on to rockin' beats!
3. CronoSeries: Chrono Trigger
Developer: Square-Enix

Akira Toriyama is popular, therefore anything he touches is also popular. Crono is no exception. Chrono Trigger still has an enormous following despite its debut having been all the way back when in 1995. He's skilled in the use of the katana as well as Lightning magic and his double tech skills include such neat effects as Fire and Ice enhanced sword strikes.
Stage Ideas: Zeal: Probably the most memorable location in all of Chrono Trigger. I could see similar terrain destruction taking into effect like with the Garden of Light.
2. Rockman/Megaman TriggerSeries: Rockman DASH/Megaman Legends
Developer: Capcom

Capcom has left this little boy blue in the dark FAR too long. The developers have already stated they'd prefer to work on the Wii and I can't think of any better PR for Rockman DASH 3 than Brawl. He's gifted with amazing jumping ability and firepower much like Samus, except with a bit more of a modern day warfare edge. (Mines, rockets, machine guns, etc.)
Stage Ideas: Deck of the Flutter/The entire friggin' world: I could see it working a bit like that one Mario ship level in Melee where you'd be bouncing back and forth between different islands and the decks of ships.
1. Cless AlveinSeries: Tales of Phantasia
Developer: Namco/Wolf Team

C'mon, you saw this coming. It's my ultimate pipe dream fighting game character that'll never be. -_- 2 out of 3 versions of Phantasia have been on Nintendo hardware and it was the start of a very popular series in Japan. If nothing else, make him a throwback character for Lloyd or somebody like Marth was to Roy.
His skills include a unique fighting style mixing both the sword and use of time altering as well as use of the element of fire and healing arts.
Stage Ideas: Euclid Arena: What better place for a cameo fight? They could even fit in the rest of the Phantasia cast into the crowd.