If you're sick of hearing Pascal's Wager (by name or not) every time you tell someone you're an atheist, I have developed this astonishingly witty response for you. Enjoy:
"Oh no! But I heard there's a God bigger and better than the God of the Bible, who has a Hell that's hotter than yours and an eternity that's longer. And He said he'd send me to Hell if I do believe in Him! And His punishment is worse. Therefore, I, by necessity must selfishly save myself (as you are doing) by choosing not to believe. But thank you for supporting my logic. I thought I was the only one."