St. Anselm's famous ontological proof of God's existence runs something like this:
I can conceive of a perfect God.
One of the qualities of perfection is existence.
Therefore, God exists.
Unfortunately, some benighted souls (I among them) have found the argument somewhat less than convincing. However, Ray Comfort, author of the best-selling God Doesn't Believe in Atheists and ex-atheist side-kick Kirk Cameron promise to prove the existence of the Most High Lord in a debate in New York City on May 5. ABC television is recording the debate and will apparently broadcast it later on Nightline. Comfort claims:
"Most people equate atheism with intellectualism, but it's actually an intellectual embarrassment. I am amazed at how many people think that God's existence is a matter of faith. It's not, and I will prove it at the debate—once and for all. This is not a joke. I will present undeniable scientific proof that God exists."
For more alleged proofs of God's existence than you can shake a stick at look here.
Disclosure: Some of my best friends are Christians.