If you could have any one super power...

A friend of mine said he wanted a small time hole so that he could go back to any time in his past and have enough room in the hole to stick his arm through and smack himself in the back of the head before he did something stupid.

Me, there are so many that are interesting but I might have to go with immortality (Highlander anyone?). It would suck to lose the ones you love but it would be awesome to see how history develops over the next 100, 1000, plus years.