For some reason, I never see this question asked, or at least not nearly enough:
"Do you wish the God of Christianity existed?"
Clearly you could guess the answer in most cases - I'm talking new atheists here - but still, I think it's important to ask the question that way. Though I also suspect most NAs would refuse to answer the question.
Another question I'd like to see thrown around:
"If the God of Christianity was here right now, what would you say to Him? Not ask, but say."
I've asked this one myself to a few people. If recollection serves, each response has just been something close to a string of expletives.