"God can't exist because of Eric The God-Eating Magic Penguin. Since Eric is God-Eating by definition, he has no choice but to eat God. So, if God exists, He automatically ceases to exist as a result of being eaten. Unless you can prove that Eric doesn't exist, God doesn't exist. Even if you can prove that Eric doesn't exist, that same proof will also be applicable to God. There are only two possibilities - either you can prove that Eric doesn't exist or you can't - in both cases it logically follows that God doesn't exist."

-- Mark