What's Your Best Comeback Line?

I was recently seated at a private dinner in a New Jersey casino, where a publicist at the table was vehemently urging me to visit the local lighthouse. I looked dramatically unimpressed, so in desperation she cooed, "It's the most phallic attraction in Atlantic City!"

Without missing a beat, I raised an eyebrow and a half and replied, "You haven't been to my room!"

Cheap, but effective--in fact, the woman looked like she wanted to drop dead on the spot.

So what's been your most effortlessly witty comeback line so far?