I had an interview in person with two people who I would be working directly under. The director, after about 20 minutes into the interview, asked what mistakes would I make if I did make a mistake. Of course I responded by saying I wouldn't make a mistake, but he insisted that I give him two instances where I would make a mistake and he wouldn't take no for an answer. Needless to say that I did not get the job.
My issue is who in the world asks that kind of question?! If you've made up your mind that you don't want to hire me, don't force me to give you an excuse.