I also asked what reservations, if any, he had about me as I would prefer to address them there and then and walk out the door with an offer in my hand (subject to salary negotiations, references etc).
I like that one, I'm going to use "Do you have any concerns about me, that I need to clear up right now in order to win the job?" at the end.
I've also got the following
"How would you describe the work culture at ——-?"
"What are the most enjoyable and the least enjoyable aspects of the role?"
"Tell me about your style of management and the reporting structure within the company"
Plus a couple more