mine would be either:
invisibilty (so that i can go to the shops or wherever and nick stuff)
the ability to read peoples minds(there would be no such thing as secrets)
to be able to fly(just for fun)
ability to stop time(so that i can sleep for as long as i like and take as long as i want doing what i want)
ability to teleport(so that i can go anywhere i want FOR FREE)
...and you may have noticed most of these powers come from HEROES...so yes, i am a fan of HEROES....