Mach Rider (Mach Rider)
Victini (Pokemon Black/White)
Chibi-Robo (Chibi-Robo)
Tingle (Zelda)
The more I think about it, the more Victini seems like a lock. According to the Pokemon Dream World site, Victini is consistently the most "tucked-in" Pokemon in both Japan and the US, so he's clearly very popular among fans; perhaps even the most popular Pokemon this gen. He certainly has moveset potential too, whereas Zoroark's "Illusion" ability might not translate well to Smash.
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Many tried to predict Boscopinions... but only starfox used the boost to get through!