I enjoy Fatal Labyrinth. Really fun, if fairly simplistic, roguelike.
Typically, I would prefer to say some sort of action-ish title, but I'm going to agree with this. Never got around to Dragon Crystal(Same type of game, but seems to be more outdoors than in a castle) on Sega's 8-bit platforms, anyone know how good that one is?
For the hell of it, I'll also mention:
Ristar - Sonic style game, except instead of running fast and jumping on things, his arms stretch to grab things, and pull enemies in for him to headbutt.
Chiki Chiki Boys - Arcade port of Mega Twins, very fun. Despite the name(CCB was the Japanese arcade title), it does have a U.S. release.
Skitchin' - Road Rash on skates, with the ability to grab cars(which is what they call skitchin in the first place), a lot more manageable(buying separate pieces of gear, instead of a new motorcyle), and feels even more beat 'em up-ish.
Zoom - Cool little puzzle game.