Fight skits are always great! Be sure to practice a lot, though, and that slow, sluggish movements can really sort of break it. A good example I found a while back of a well choreographed fight would be this
Just be sure to check in with your convention's masquerade rules. I know for my local con, due to the nature of the stage being a temporary fixture (aka, a flimsy piece of crap), none of the skits could have sudden physical movements, jumping, or a lot of people dancing on the stage at one time.