I have never thought of such a thing, I guess I have no purpose, I guess you make you're own purpose after all having a predetermined purpose would imply destiny, in which I don't really believe, I prefer to think that life is nothing but coincidence, chance if you will, destiny would be dictated by nothing other than circumstance you find yourself in and what you decide to do within it.
But if I had to choose, I like to think I'm making the world a better place by being awesome, by which I mean being a good person that goes out of his way to help other people, I mean you only get one life you may as well do something positive with it, and besides you're life is less than a mere blink in history, so why not try to make that blink as enjoyable as possible to everybody.