Wow I can't believe that no one has said X-ray vision yet. I'd want it. But only through wooden doors. Then I could see what the bad guy's are doing on the other side of the door as long as it as wooden.
I would actually like to be able to control all matter. Imagine it. I could like take metal and reform it into a plate or a boomerang. I could take a person and turn them into a cube.
I would be so evil. Control-all-matter MAN.