Oh, you are wicked. Here's some more off the top of my head.
* raise your hand and when called upon, announce that you had an "accident" and you will need a volunteer to stand behind you while you walk the hallways to the ladies'/men's room to change your Depends.
* Count the teensy, microscopic holes in the ceiling. Out loud. In Spanish. Or perhaps Italian? 
* Scream out, "GRANDMA! PLEASE DON'T HAUNT ME ANYMORE! I DIDN'T MEAN TO STEAL YOUR FALSE TEETH AND BURY THEM IN THE BACK YARD!"
* Pick your nose and flick the boogers across the room. Ten points if you hit your enemies.
* Write love letters to each member of the class and sign them as being from other classmates. Make it interesting by pairing up the football captain and the class nerd.
* Fart. Loudly.
* Blame the farts on the person next to you by requesting that you change seats every time you rip one.
* Put on your Harry Potter cape and wave your pen (wand) at your classmates, chanting "Wingardium Leviosa." Then, try not to pass out when one of them does indeed levitate.
* Dial your teacher's cell phone, then when he/she goes to answer it, hang up. Wait two minutes, and then repeat.
* Toss a match out the window and then announce that the dean's car is on fire.
Heh heh...need I say more?
