"You're not religious, are you?"
It's delivered in an accusatory tone, as though the correct answer is obviously no.
I hear this question on a regular basis, usually after someone I don't know very well has said something offensive about God, Jesus, religion, fellow human beings, etc. It makes me instantly defensive, and I almost always trip all over myself trying to figure out what to say. If I quickly rearrange the wording of the question and remove the implied value judgement, the question is "Are you religious?", the answer to which is yes. But that's not the question. The question is "Are you one of those crazy right wing fundamentalist nutjobs that forwards a lot of email about God and country and believes that everyone is going to hell (most specifically gays and people who don't believe exactly the same thing as you do) and that children should pray in public schools and that we should ban certain literature from all libraries and that life begins at conception and abortion is murder?" The quick and dirty answer to that question is no.
In any case, if I ignore the value judgement and answer yes, I usually either find someone apologizing and then continuing to explain how they think that religious people are crazy and then go to great lengths to describe their nuanced views while I nod and smile and they incorrectly assume that I have no nuanced views because I've described myself as "religious." That, or they immediately shut down as though there's no reasoning with me and this is just something we shouldn't talk about.
If I say "no", or try to dig more deeply into the question, I get myself into trouble. First, because that answer isn't true. Secondly, I don't always feel up to explaining myself and serving as the singular voice of all Christians in the world (which is akin to someone asking me to speak for all White people in the world, or all women in the world, or whatever). My family has a long and complicated history with the Lutheran church in particular, which has profoundly affected my relationship with the institution, and is not something I generally wish to discuss in everyday conversation, particularly when dealing with someone who is more interested in polarizing than talking with me.
Despite what anyone may see on TV or hear from one of our vice presidential candidates, I am not going to pull a Bible out of my back pocket and start proselytizing or speaking in tongues if you tell me you're not religious, or if you take the Lord's name in vain, or if you use profanity. I would, however, appreciate the same respect in return.