I just thought of something that would be amazing in Punch-Out!!

[Majin-Tenshinhan]

Cactus said:
My money is on either Giga Mac, or Mr. Dream

There's simply no way it's Giga Mac, since it would be completely pointless for that to be under embargo until the game's release. Mr. Dream is possible, though I don't see why they'd want to make such a big secret out of that.