I think about it often the last year. But I want a really super super power, almost a divine one! My idea is to have the power to remove all the weapons, all the guns, all the machines that produce weapons and everything related from the earth and throw them to the sun. If people still want to kill each other after that, they can grad a wooden stick and break each others head, at least they won't destroy the whole planet doing so. But this is just a fantasy :)