I laugh.

"ill be waiting for ya with a picnic basket"

"Awesome, see you there".

You show me ONE person... just one... who is suffering in hell, and I'll listen to what you have to say.

It's your hell, you burn in it. I choose a different path, thank you very much.

I tell them that's why I'm getting cremated. HAVE TO GET USED TO THE HEAT! Don't really care what others think. If you don't like my views, leave me alone.

I just say, "I hope that happens to me"

Why would an all loving caring God want to punish the people he loves.

"You first!"

Laughter is always appropriate.

I ussuallytry to just walk away from them, you can not argue with a fanatic, its not worth it.

I laugh.

Possibly comment on how it'll be a party and that with all the other scientists we'll have probably figured out some geothermal powered cooling system. If they persist then I'll pull out my notebook and start explaining science to them until they get bored/frustrated and walk away.

I say that heaven and hell are here and now, that I am responsible for my own elevation or demise in every moment.

I tell them that if a god or goddess would punish me for following my heart, for being kind and understanding toward others and trying to make the world a better place, then he/she/it doesn't deserve my adoration.

I simply tell them to see help for their mental problem.

It depends on who's there. If going to Hell means I can meet Aristotle, Nietzsche, Evariste Galois, Alan Turing, Carl Sagan, Jean-Paul Sartre, and more of my heroes, then I tell them I can't wait to go to Hell. Also I'm pretty sure Hell will have some kick-ass heavy metal playing 24/7.

I can not take the person or the threat seriously. I do the eeeeeewwwwwwweeeeee spooky boogyman gonna getcha creepy fingers geture.

"Um, no thanks. The Flying Spaghetti Monster has better plans for me."

I try to be respectful as long as they are. I tell them that I don't believe in their afterlife and its my concern not theirs. If they get belligerent, I try to separate myself from them and if I can't I give them the old "its your hell, you burn in it".

I don’t think I’ve ever been threaded with hell, etc., but if I was I’d let them know that I’d rather chill with Satan any day.

I laugh at them and politely suggest that they should not be deluding themselves.

i discuss them that there is no evidence on the punishment existence.

Has not happened, yet.
But I'd be inclined to tell them that saying that is naughty, and so Santa won't bring them presents.
And try to explain that threats of Hell make as much sense to me as my Santa threat does to them.

Can't say that I've ever been threatened with that, or it's been so long, I don't recall. I would assume if someone did tell me I was going to hell, I'd probably just chuckle and walk away...

"If you're going to heaven I'd rather be in hell!"