What bothers me most is when a candidate gives off a "this is below me vibe". I tend to start with quick, easy questions and work toward much more difficult ones. Candidates often act as if answering these easier questions is below them... And then choke on the hard questions.

To me, acting haughty is a good indication that you're going to be a pain to work with. You're going to make a fuss when asked to do easy work, rather than just getting it done and moving on to the more interesting things.

That's my pet peeve and the pet peeve of several others I know, so apparently it's fairly common.