My personal recommendation is to ask questions that a first year consultant might ask and less an interviewing candidate. The last few mins for questions is fully under your control to leave a positive (final) impression!
Beyond the typical questions around the interviewers experience, office culture, projects, etc., as a candidate, I tried asking questions that made the interviewer leave the interviewing feeling they could see me joining and being successful at their firm.
A few examples:
+ Beyond hard skills and experience, what do you look for when you're staffing for your project? What differentiates a consultant you want to staff again on your project?
+ The diverse experience at X is something I find compelling but I'm curious to hear about your experience and advice on how to best navigate the firm?
+ What should I prioritise/look for in my first few projects?