Let's see now... first I would find the one person I love truly and watch them from a rooftop Assassin's Creed style, then I would go and activate my invisibility powers and do what Yahtzee suggested on fullyramblomatic dot com then I would go and beat the stuffing out of some people I don't like and hang them from something high up.
Then I would conquer the world somehow and turn it into a utopia. Then build a paradise out of Australia. Then build a real-world edition of DooM and force Michael Atkinson to play through every level created by iD just so we can see him fail spectacularly.
There's plenty more, but I've got stuff to do.
-Frosty05