When being an interviewer/ee over the years, my favorite question to ask was for the potential hire to tell me the most difficult obstacle at their last job, and how they delt with it? This question was asked after a series of mundane ones, intended to lull them into a comfortable dialouge.
This showed me two things right off the bat:
1. How quickly they could think on their feet.
2. If their response started with any kind of negitive, it was an immediate end to the Q&A, as it showed their true character.
HTH,
Holly