Me, now: I think Brash the Bear would be a cool character.
*After E3, five years later*
Those in Denial: Brash the Bear was an unlikely guess, but still a possible one!
As a matter of fact, I've "talked about" Brash the Bear, a character from a series that is heavily focused-upon for Smash newcomers, twice now in a high-profile thread with hundreds of viewers each day. This is in comparison to one guy who "talked about" WFT once in a four-post topic that was buried and forgotten about until it was dug up by people who, in fact, were looking to fact-check the denier claims that people were "talking about" her, not those deniers themselves (this being indicative of them talking out of their arses as usual, of course).
Point being, Brash the Bear is officially now easier to guess than the Wii Fit Trainer was.