Here is a question that actually makes my JW aunt feel uncomfortable.. er, rather, she admits that this question makes her uncomfortable.
A very prevalent argument for the existence of god is the apparent complexity of the known universe. This complexity, believers say, is proof positive that the universe was created. They ask, where did we come from? We couldn't just appear out of nowhere, the big bang can't actually explain things. Things can't spontaneously increase in complexity, everything has to come from somewhere, and that somewhere has to be at least as complex as the known universe.
I say, then, if "everything has to come from somewhere", where did god come from? In arguing that angle, you have implicitly presupposed a "creator of creators" and also a "creator of creator of creators" and so on, each preexisting and more complex than the one after it.