Never much cared for that "So, what do you do" question; it ranks right up there with "So, tell me about yourself". I never quite know how I'm expected to respond to such things. Add the words "for a living" on to the end of that first one, and you might get a more sensible response. "Where are you from?" is another classic, which, depending on my mood, might get something snarky like "my mother". I think, though, that the worst one has to be "So, why aren't you married yet?" Is there anything more tactless?