I got the idea from my college days, when I met my first atheist. I told him he wasn't really an atheist and I could prove it. He got all huffy and challenged me, so I pulled out two quarters, fifty cents, and said, "If you're really an atheist, then sell me your soul for four bits. Since you're absolutely sure you don't have one, you make infinite profit, and there won't be any higher power in the picture to enforce the deal."
He sold me his soul, but by the end of the semester he was begging me to sell it back to him. Turns out, he didn't want to take any chance. My atheist friend was really an agnostic. I made enough money on the sale to get me home for Christmas.
I've met only one true atheist since then, and currently own his soul. Every Christmas, I let him know it's still in…ah…good hands.
Merry Christmas, John.