Do you have a question for me?
Almost any interview ends with this question. The interviewer wants to clarify any remaining doubts that you may have. You can ask whatever you want, but pay attention not to ask something stupid or something that requires a long answer. You can ask details about something that the interviewer said but that was not very clear, or you can ask for their personal opinion about you. Or, you could ask something like, How did you come to this company? What has been most challenging for you? If you have nothing to ask, then don't ask. Simply say something like, Well, I have to say that you've answered all my important questions. Thank you for your time!.