It depends on what kind of day I'm having, far out, baby!

If I am in a "I have to learn everything now! Now! NOW!!!" kind of mood, then I'd go with super-speed so I could read everything in the world until I understood it.
If I'm in an "alone" kind of mood then I'd want to be able to fly, because not many people know how to fly, and those who do know use airplanes, so they probably wouldn't open the window and ask me for Grey Poupon.

If I was horny, then I'd want X-ray vision... If I have to explain that one to you, maybe you're not ready to understand.

(I'd get to see everyone's underpants!!! Underpants! UNDERPANTS!!!!!!! ooohhh, think of the posibilities... tee-hee!!! ...and they would never suspect that I knew that they were wearing fuzzy lime-green high-cut briefs that have "Let's Lambada" written in rhinestones on their butt.... ahhh... the lambada.... er, that is... ummm... I want to see people naked.... Yes... that's it... naked....)