They are advanced students who have been together for five terms. Even if you come up with the ice-breaker to end all ice-breakers, they may have had it inflicted on them before. I would just introduce myself very briefly, and then get each student to introduce the student on their right and tell me one interesting thing they know about that person. This is a little different from the self-introductions they have probably done many times, and might bring up an amusing little anecdote. It will also give you an opportunity for follow-up questions if you wish.