Here are a few I've heard or seen....
Filling up wrench handles with shock oil
Filling up padded chairs with Paragon (hear it burns...LOL)
Cutting a chair apart and then CA it back together just enough until someone sits in it
Drawing a penis on every single item in ones pit; including wheels, tools, boxes, pit boards, cars, bodies, etc.....
This was all done at 1 race and I'm sure I missed several
Another brutal one was a CA'd body onto the car along with everything in the pits