I laugh at them & tell them that their ridiculous delusions have no affect on life (or after life, for that matter).

I get all choked up and say "I'm Sooooooo scared"

That has never happened to me. Ever.

Laugh.
Maybe say, well all my friends will be there, if they tell me I am going to Hell.

I say " you wanna get butt naked and wrestle?"

I tell them, “Sorry, Satan already offered me a job in Human Resources!” “Now run along, I’ll see you later.” With a devious smile.

I would just laugh at them and tell them you will be sent to the North Pole because I would rather be hot than cold.

How am I supposed to take the threat of hell seriously when I fundamentally don't believe in it? It is a specious threat. I suppose my response is "oh."

See you there. Then laugh maniacally

Hah, that puts them on the ignore list immediately.

I tell them I am a New Thought Christian(which I am) and so I don't believe in Hell. Further the Hell they believe in was invented during the Dark Ages by Dante. Jesus wouldn't have know what they were talking about. If that didn't work, I would probably beat them over the head with the very scripture they tried to attack me with. (Metaphorically of course). A good New Thought Christian would never do this, so I guess I have a ways to go.

Surely the only valid response is laughter?

I just laugh. I can't say it won't happen but doubt it so strongly as to ridicule this God of theirs. I tell them that I hope to actually have that Judgment Day so I can look Thou in the eye and ask what kind of sick motherfucker Thou is? Was the experience I just had to endure really necessary or some kind of uncomfortable joke? That usually shuts them down but gets a horrified chuckle.

"if you dig a pit for someone, you end up in it yourself"

Sad that their religion is based on reward and punishment. The only hell is theirs.

If Pope Francis says I can get into heaven as an athiest, just trying to do good and living by my own moral code, then that's good enough for me. As a Catholic, I would be expected to repress my sexuality. As an atheist, I don't have to.

And the scoreboard says:
Atheism 1 - 0 Catholicism

Ok, see you soon.

"Demons, sodomy, and so much heat the clothes are likely to come off. Doesn't sound too bad to me."

Such a threat has about as much meaning to me as if they'd exclaimed "bopity bop plobalop wibble wobble woo", although slightly less amusing.

I generally just shrug and ignore, unless in the mood to have a lengthy and tiring debate where I request objective evidence for the claim and then have to exhaust myself explaining how citing a religious text as proof of it's own accuracy is a circular argument and not an objective one.

Hell is quite a nice little town in Norway, and I'm very fond of Jahannam on toast.

Varn: Thanks for the AC/DC!

Laughter!

When someone informs me that according to their beliefs I am sinful/immoral/going to burn in hell?

I let them know that as a Taoist, my belief is that they are perfectly doing what they should, and that I believe they should go on believing that if they want to.

I am not that devout a Taoist, but it does take the wind out of a crusading monotheists sails.

Disbelief, and an uncontrollable smile

It’s actually difficult to recall when I’ve been ‘threaten’ like that … and it generally came from the craziest of the crazies. One religious nut wearing a sign-board and using a ‘bull horn’ in downtown Portland (Ore) as my young daughters and I waited for a light rail train didn’t like my questioning his rant... It was a good experience for them to witness the base hatred in such people.

The other was after my mother and I stopped to take on the religious crazies picketing an woman’s health clinic, also in Portland. We’d worked them down a side street… and when they finally realized what we’d done, really got pissed! Kept em out of the public’s eye for maybe a half hour We’ve some serious ‘hell time’ if they’ve any pull! But Mom’s always said, ‘she wants to end up wherever Pat Boone isn’t!’

I tell them if they don't leave me alone I'll rip their face off, laugh and walk off, this is Waco, this is Texas, if they want to go pray for me, let them.