Complete & conscious mental control of spacetime and be able to order all forms of matter, known and unknown, to suit me. To have my consciousness contain all that exists. All under my complete control if I so desire. To be all knowledge, all information...
Hmmm... I suppose that would make me God, huh? I'm probably forgetting something...
Then again, perhaps that would be boring after a time and I'd incarnate myself in the flesh just to play with my creations. Hmm... that would be broing after a time as well. Where would the challenge be?
Eh, overthinking as usual.
I guess being Superman would be adequate.