I'd want to have the ability to read minds and scan memories. It's an extremely powerful ability when used properly but it's not so overpowered that there would be no challenge in accomplishing my goals. An auxillary ability that allows me to telepathically copy the knowledge and mental abilities of others would also be nice. For example, being able to instantly master Muay Thai, become a mental calculator, or learn everything that an individual knows about a language simply by being in contact with them.
Other than that, Reed Richard-style super genius would also be nice since it would allow me to obtain just about any other power that I could wish for simply due to a mastery over technology.