I tell them I don't believe in Hell.

I laugh at them.

General bemusement, a wry smile and fleeting nagging doubt.

I'll tell them if they've ever worn blended fabrics (nylon/cotton/spandex/etc.), eaten shrimp, thought about doing anyone without being married to them, masturbated, or broken any of the laws listed in Leviticus (and there are PLENTY), then I'll see them there. Bonus points for me if I can point out a few that they are currently breaking. They usually come back with the whole Jesus died on the cross for my sins, so I can eat shrimp and pork... to which I just laugh and say yes, Jesus died so we can all eat bacon... it usually dies down after that.

easy.
my only child is dead.
i'm already there.
suck it!

I tell them religion was created for man by man for the purpose of control and to explain things they could not explain. I also ask them which "GOD" there have been over 3,000 throughout history.

There's no such thing as hell so why should I be scared of it

I calmly tell them, "I'll see you there". I have come to find there really is no point in continuing a dialogue with someone when they throw out what they consider to be their trump card (you're going to hell!)

I laugh.

The concept of heaven and hell, as opposed to the house of God, only dates back to the 2nd century. The idea behind it was to create a carrot and stick model of reward and punishment in the afterlife, for the purposes of political control over the people. It is on some level a little bit clever, in as much as it is predicated on the notion that all of your behaviours are observed by an unseen god and you can get away with nothing. As a concept it has one advantage over the previous system in which reward and punishment took place in this life, specifically it reduced the necessity for the death penalty over minor infractions, since now is possible to be punished after death. As a means of controlling behaviour it does however have one significant drawback, in order for the heaven and hell hypothesis to work in reforming criminal activities, the concept of forgiveness through repentance is a necessary component, and therein lies the rub. Because you can be forgiven by repenting, it is possible for the devout criminal to imagine that he or she holds some form of divine get out of jail free card, since even minor punishment here on earth can wash their Souls clean. Therefore, since they can be absolved through repentance, they imagine they can look forward to an eternity of pleasure in heaven despite their crimes as a result of earthly incarceration and repentance. Thus the inspiration of being good for its own sake, of being good to create a better Society for once children and grandchildren here on Earth, and of genuine fear of earthly incarceration is lost. This is precisely why 98% of the prison population is religious, it is also why atheists make up less than 2% of the prison population.

Laughter

No one who knows me would try that shit with me. And anyone who doesn't know me will find out fast this ol' retired Lawyer isn't shy about the matter.

If someone insists on giving me their opinion about my ultimate status before their gawd, I'm happy to disabuse them of their idea I give a shit about their opinion.

I tell them I don't believe in imaginary places.

Caveat: When people tell me I will have to "stand before god and answer to him." I say, "IF I stand before god, he will have to answer to me."

If heaven is full of Christians, no thanks. I'd rather be in hell with the scientists who will bring AC, the cartel bosses who will bring the drugs and the bartenders who will mix up the drinks. I'd rather laugh with the sinners than cry with the saints.

Are you my guide?

I hold a solemn poise. A straight face. Thinking how I once used this against people i thought needed a little nudge in my direction, i thank them for their concern and move away from them. They have a conviction working on their heart. They want to save me from a damnation. I understand them. I don't challenge their belief or make any statements against it. Our belief comes gradually with some people. It scares others. Just avoid the argument and be polite. Your knowledge and advice is not wanted.

Obviously its uncomfortable to hear any threat of religious punishment, real or otherwise. I have found that calmly and politely explaining to them that they can't threaten you with something you don't believe in. Now you have to realize from their perspective that they are attempting to save you from hell/damnation. When they say they are trying to save you, say you can't save someone who doesn't subscribe to the same worldview.

Educating them politely and non-judgmentally may actually slightly open up their worldview and not threaten the next person with religious punishment

I tell them that heaven has always scared me and that I think I'd be happier elsewhere. If that doesn't scare them off then maybe we can have a decent conversation. If they start to yell, though, I just walk away.

I just laugh. I can't take them seriously.

Don't care as nothing will happen, heaven and hell are,in my opinion, hoaxes!

I don't care as heaven and hill don't exist!

I almost never encounter this, as I have never been a Christian and do not surround myself with such people. But when it happens, depending on how pugnacious I'm feeling, I will either 1) laugh; or 2) Say, "screw your god, let him strike me dead right now if he exists".

I explain how that is manipulative emotional blackmail and aks them to prove that claim.
Only people online do this, probably because they are afraid of getting told out in person.

I tell them I don't believe in Hell or any of their beliefs.

I go and hide in my coffin.