Coincidentally, I've recently been schooling my daughter on the proper answer to this question. Everyone chooses invisibility or flight (ugh, sprout an imagination) or some other strange thing.

All I want is omnipotence. As far as I am concerned, it is the only correct way to answer to the question.

As far as how I would use it... For my own evil purposes, I assure you. Revealing one's plan too early is many an evildoer's fatal flaw.