Think Schwinn Varsity. Ugliest color you can find with chrome fenders and mousetrap rack. Put a couple of Justin Beiber stickers on it and one strange colored tire on the front. You probably won't even have to lock it.

Really though, old 10-speeds and steel rigid framed MTBs make good college commuters and you won't lie awake at night wondering if you should have added just one more lock.