I always thought a castlevania beat em up style A la Final FIght would have been awesome. Multiple enemy combos and such would be nice, like punches and kicks integrating subweapons and the whip with normal hand to hand combat. Although, Dracula and Death would probably not look as cool with those types of backgrounds.
Maybe a Street fighter Alpha style game featuring 20 good guys and 10 bad guys. That'd own. I know there's mugen... but it's not really that good with castlevania sprites.
ok, make a castlevania game with a whip in one hand and a scythe in the other. Scythes are just great.