I don't remember where / who I stole this from, remember kids, there's no originality in banking, but my favourite question when they ask: "Do you have any questions for me / us":
What is it about my resume and experience that interest you.
It's a beautiful question, makes them recite a list of why you're awesome, right before you leave. Aside from the ego stroke, it makes them verbalise about why they should hire you. Also, their answer lets you know what they are focusing on, so you can tailor your follow-up and prep for the next round interview.
What are your favourite questions?