Well, I always thought it would be neat to have a body partially composed of advanced nanites. The lil' buggers would always keep the body in tip-top shape; eating and sleeping would become unnecessary. Damage would be instantly repaired, and you could shape your body into weapons or armor as needed. You could also make a few copies of yourself composed entirely of nanites to work at a factory 24 hours a day so you wouldn't have to work. Not exactly heroic, but useful.

-Balanthalus

PS: I've been wondering; could someone with a good knowledge of quantum mechanics tell me if the Heisenberg Uncertianty Principle makes nanotechnology theorecically impossible? I'm a little fuzzy on at exactly what scale it becomes important, but I'd assume if the nanites had to rearrange the subatomic structure of atoms there would be a problem.