I have the be all end all best power in my opinion. I would have the power to give and take immortality at will. This would of course include myself, and have a proper immortal, none of the having to chop off your head, or you have to cut me into tiny pieces and spread me across the universe.( I wouldn't be able to help but feel like I'd be the antagonist to someone drawn with over sized pointy hair). Either grow what ever back really fast, or just be impenetrable. Just think about it, being able to spend eternity with anyone, being able to live forever. Sure you would kinda get a god complex, but if you were true and noble, just think of all the good you could do, i suppose you'd need a gun or something. There are some loop holes I'd like to clear up. One being pain, which would be rather inconvenient, so lets say aside from emotional and non physical pain, you feel basically nothing in terms of pain. Also aging, which I think should just stop when immortal is turned on.