Laughter and merriment. Followed by walking away.
I tell them to prey for me. I don't think it has had any effect thus far, if indeed they have.
"That's fine by me. Supposedly your hell will be the best place to be!" I also like to say "That's not what my religion says!"
Especially the 'Hell stuff', I really like to barbecue everyday!
I try not to get into a debate with those of faith. People of faith tend to believe what they have been taught, regardless of proof. You can argue with someone who considers evidence. You can’t argue with someone who blindly believes without some sort of proof. I usually take a chapter from their book and turn the other cheek by casually changing the subject. Or smile and nod until they get tired of talking.
You realize you're threatening me with something that doesn't exist, don't you? You might as well threaten to punch me in the aura and poke out my chakras.
Then again, if your Hell and Heaven did exist, I can't think of a torture that would be worse than being surrounded by people like you.