Ahh! This is a very difficult question to answer. There are quite a few powers that come to mind, including: telepathy, telekinesis, shape-shifting, super strength, teleportation, and the ability to steal other people's powers(only if there were other people with powers). If other people had powers, I would take that ability HANDS DOWN! If not, I would probably chose telepathy even though telekinesis is almost as tempting. I would really like to know what other people think but moving things with my mind would also be awesome. Shape shifting would be very useful. The whole enegmatic, mysterious persona is very enticing to me and I would like to experience that. Super strength would be cool but kind of boring at the same time.
I would probably just pick telepathy because controlling the minds of others, reading minds, and other mind-related abilities would be the most fascinating to me and I think that it wouldn't get old and boring as quickly as other powers would.