At my school there is a student that all the instructors find to be 'difficult'. He thinks he knows everything and is constantly challenging his instructors, which often disrupts the class. At first I found this student to be difficult myself, until I noticed that whenever I agreed that he was right about something he didn't interrupt again for about half an hour. This gave me an idea, and from then on I tried to ask him questions periodically that he would be likely to get right, and this has kept him engaged in the class and no longer disrupting the flow of discussion.