Bring a small cactus to class with you. Raise your hand, and when you're called on, say that the cactus has a question. Turn and look at the cactus, as if you're waiting for it to say something. After a few moments, shrug, and wait for your professor to move on. Do this once a day, and become increasingly irritated with the cactus every time, sighing heavily and giving it evil looks when it fails to "speak." When you leave the room after class, start yelling at the cactus, "I can't believe you embarrassed me AGAIN...."
Bring a vacuum to class. Halfway through class, stand up and start using it. If your professor objects, explain that you "can't stand sitting in this pigsty any longer." Keep vacuuming, grumbling angrily.
Brush your teeth during class. While doing so, raise your hand as if you have a question, and mumble your question incoherently while brushing, spewing toothpaste all over the place. If your professor objects to your actions, go on a tirade about proper oral hygiene.
Carve a bust of your professor out of cheese. Tie a ribbon around it, and present it to him/her at the beginning of class. Demand extra credit.
Come to class every day wearing scary Halloween masks. Try to get your professor to guess who you are. Shoot him/her with a water pistol, scream, and run around the room knocking things over. Say, "Pretty scary, huh?"
Dispute everything your professor says, no matter how simple. Try to get him/her to "prove" everything to you. Rant and rave about what a big liar your professor is. Yell at students who are taking notes, saying, "Stop writing down all these lies!"