I just had this happen to me.
I replied (my first gut response),
"I have no idea you're talking about."
You guys had some better ones, but I just wanted to share.
oops meant to say:
"I have no idea what you're talking about"
It was off the top of my head...
I'd hope for a funnier less mean sounding reply if it happens again.
I should have said, "Oh he says that to all the girls."
Jesus loves you, or is it just gas?
He doesn't call, he doesn't write,
I think he jerk me 'round for spite!
Yeah, Jesus loves me ... that and $0.55 will get me a cup of coffee from the machine at the commissary.
"Thank you". If you want to go further, "that's nice of you but I don't believe in superstition", "but I appreciate your good heart and loving wishes".
I like this one from The Big Lebowski, "Nobody fucks with the Jesus!"
I remember hearing a preacher in church tell the congregation that when God comes to you, he usually comes to you through people. Now it's true that inscripture he does, but it's also very common in the Bible for God to show up and slap some bitches for their disrespect.
My advice would be to use logic and be nice about it. Although they're being presumptuous, annoying and naiive when they say "Jesus loves you", I think it's more effective to get them to think about their reasoning rather than just piss them off. That way you have the chance to bring them to reason instead of polarizing them further into their own faith.
"Why doesn't he tell me himself? Why doesn't he come down to earth, sit with me in the darkest hours of my life, through the loss of friends, the pain of grief, the death of loved ones, the genocide of my countrymen, the injustices of our time, and comfort me? Why doesn't he answer all the questions I asked as a child when I believed he was there? When you talk to him next, ask him that. I'll believe in your god when He gives me a reason to. Not you."
You can shorten it if you want, just an idea. People telling me Jesus loves me is especially offensive to me because I value love so dearly, and think it should be respected as a verb, not just a feeling. So when people tell me Jesus loves me I rage at them for comparing Jesus to the love of my father, mother, friends or girlfriend, who have shown me more love, care and reason to believe in love than Jesus ever has.