I like "what do you like about working here?". Extremely useful if you have multiple interviews, as you can ask the practical stuff in the first round, but at second round (or in the case of my current job, at third try of getting into the company), I often get stumped. This gives you a simple easy question that can be quite revealing. I chose not to take the job where they side-stepped the question.

Also, do not turn up with a list of questions on paper and pull it out when they ask you, the interviewer will have The Fear that the interview is about to overrun massively. But it is ok to ask questions by email if you think of something afterwards, as long as it's straightforward and factual. Shows you are still thinking of them

H