Ask them if they donate money to a political campaign and if so just ask for a similar donation or to simply pray for their politics

Depends on my mood, and the apparent intentions of the person. If there was a genuine tragedy, and the person actually is showing concern in more ways than empty words, then it's fine, and I thank them.
After all, if they really are praying for me, then they are projecting positive energy in my behalf..always a good thing.

But if it's done in a patronizing manner I might say, "There's no god, but thanks for the good thoughts."

This shocks them into silence since they can't think how to defend god except by quoting the Bible, which I just said I don't believe. I then act like I remember something and leave the room before they can reload their brains to attack me.

I never hear it. People know not to say it to me.
I am a forthright atheist, so they learned quickly not to waste their time.

I just tell them, thx whatever floats your boat

Even though I am emotionally and intellectually rolling my eyes about being prayed for, I have been known to say, "Thank you. I know what it means to you to say that." ... They mean well, but their idea that they are doing anything to help is simply wrong.

I can't remember the last time...but usually don't get into that type of situation...keep doing what u feel is right..

I say, "Whatever"

it depends who they are and why they’re saying it. context matters. if i’m experiencing a tragedy or illness and someone who loves me says they’ll pray, i’ll probably thank them. it sounds the same to me as them saying they’re thinking of me, and i find that sweet. if i’m in a really bad place mentally, it’s possible i’d snap at them, but that could happen with anything, and i would apologize after. if it’s someone saying they’ll pray i stop being an atheist or some shit, i’ll tell them off. unless it’s like... my grandma. then we go the smile and nod route lol

Same here they are being nice and concerned

I agree with you. I cannot stop anyone for praying for me.

Hmmm... well, it's going to depend on the context and the audience. In very broad, sweeping generalizations:

If someone I know is saying this to express concern and leaves it at that, I would accept such as it was intended - a wishing well.

If someone I don't know is saying this to express their disapproval of me, I would tell them under no uncertain terms where they can go and what they can do to themselves when they get there.

Fortunately, the vast majority of people around me fit into the former category and very, very few have had the misfortune to fit in the latter category.

How?

"You will always be in our hearts and mind"

Same thing without the religious connotation.

Say thank you, Then say but cash works even better though.

Sometimes I nod and ignore it or, if I'm feeling a bit combative, I'll ask them "For what purpose?" and challenge them further based on their reply.

I usually say, "Please don't, it's rude."

Its different here in the UK, I have never heard it said. I think that here, even christians would think it impolite to offer to pray for someone without permission, and would think it vain to tell people about it if they did.

It depends on who it is. My mom I usually say I wish she wouldn't. If it is a friend of mine I will pull something out like I don't think it does any good, or is a very tangible idea.-or crack a joke- if I don;t know the person very well I usually side step it .

I immediately clothe line them to the floor then elbow drop them then do a moon somersault to finish them off. Get up brush my self off look around the room and ask if anyone else wants to try and pray for me?

Typically I too smile and nob and thank them, but in my head I'm saying, "Sure go ahead. Prayer hasn't ending starvation, sex slavery, or cancer but maybe it just might help my pathetic ass!" My inner self is a real asshole sometimes.

Nobody says that to me. Should I be glad?

I say "To Whom?"
If they respond I hold my hand up (not matter what God) and say "No thank you, I am not in need of sorceries"

During the holidays I respond with "and Merry Mythmass to you!", which gets universal head tilt, like dogs hearing farts, a "did I hear that right?" expression.

I, too, just smile, say thanks and walk on.

I'll say....Good voodoo to you too.......They don't get it right away sometimes but some do and they aren't sure how do deal with it

How about telling them to pray that no one ever says they'll pray for you again

The same way I do when someone tells me to have a blessed day. They do mean well and I accept it as that. They are harmless words. Now if they start flinging holy water in my face, then I might be offended.