I've always wanted telekinesis, honestly. The number of times I've wanted to turn off the light without having to get up, needed a third hand for something, wanted to type or use my mouse but my wrists hurt, or just need a little more heft to lift a heavy thing is just ridiculous. If you have enough juice, you might even be able to levitate, or even sorta fly. (Flying is just lifting yourself, and then moving yourself from place to place, right?)
Although shapeshifting would be a possible second choice, for so, so many reasons.