Maybe Donkey Kong takes out his coconut shooter and blasts the crap out of everyone. And Metaknight could take off and fly around the screen, slashing everyone he comes into contact with with a one-hit-kill (like a Pokemon-esque move in SSB). Fox could summon his crew to come blast everyone away. Snake could...hmm...I can't really think of anything if he won't have guns, but he does have a rocket launcher, so maybe he does 3 rapid fire rocket shots on someone. I can't think of these easily, but those are my ideas.
umm what about for gannondorf he would turn in to tp gannon (the big boar)
and charge everybody the warp back and charge again the revert back to gannondorf
and snake would go into a metal gear