Immortality of course. Though it may get a bit boring when the Earth blows up and I'm left floating through the universe for the rest of eternity. At least until i'm found by aliens or turn so insane that I don't notice the desparity of my predicament and of course i'll have a brilliant seat for the inevitable end of the universe.
But if i'm found by aliens they'll undoubtibly be mystified by my ability to survive anything and probably make me a test subject for many disturbing experiments which will turn me psychopathic. I'll end up being locked away and forgotten until their civilisation finally falls and I escape, hijack a spacecraft and find a planet where the alien girls are easy on the eyes and settle down. I'd move on to a younger alien girl when my current one becomes to old, and slowly my human DNA would permeate into the alien DNA and the best of both combine until over the course of generations a new stronger human race will form, of which I will be the eternal ruler.
Acutally scratch that, I want the power to turn things into cake!