Theists: What is the most compelling argument you have heard for Atheism?

[SteveII]

I am not interested in arguing about other religions. I asked specifically about Christianity. 

1. If you are talking about Christianity, you are painting with too broad a brush to make a point. Christianity does not attack science. Science has nothing to say about whether Christianity is true or not. If you think it does, you are wrong somewhere in your understand or logic. 
2.  Untestable, unfalsifiable theories. 
3. You couldn't possibly know that and your opinion doesn't much matter to me.

Of course you are not interested in arguing about other religions because magically you picked the correct one. So what, get in line take a number. 

Science most certainly DOES have something to say about the claims of Christianity. No such thing as a magic baby born without a second set of DNA. Humans also do not survive the death myth as the bible would imply. Without those two most important stories the bible claims about the Jesus character, you have nothing. [1]

But again, funny how you rightfully reject the claims of other religions but refuse to aim that same logic at your own book. [2]

Nope sorry, I cannot take a book seriously that makes claims about men magically popping out of dirt, women magically popping out of a man's rib. A book that treats the sun and moon as separate sources of light, when science proves that sunlight bounces off the moon. I cannot take a book seriously that makes claims about talking snakes, talking bushes and talking donkeys. The flood never happened, but if we assume it did, it is an immoral act of genocide, and the buyers of that tripe would be still stuck with a limited gene pool in the Noah Family at the end of it. [3]

Of course you aren't interested in debating other religions, don't feel bad, most humans aren't either because everyone thinks they got it right. Tell me is Thor a real god because we observe lightening? [4]

1. No, it really doesn't. Christians claim these events were supernatural (not-natural) in cause. Since the supernatural cannot be examined by science (by definition), it cannot comment on the cause. It can only describe the effect. 
2. I believe my religion is more evidenced, more plausible, and better describes the real world than others. It does not matter (nor concern me) that you cannot distinguish between them. 
3. Very original and sophisticated arguments. My faith has been shaken.
4. Yes. That is the reasoning I use and it can easily be applied to Thor. Good job at zeroing in on the issues.