If you say they're throwing paper on your desk, I have a good idea.
Take the pieces of paper that they're throwing, write little messages on them, and return them to the sender.
Some good messages would be,
"Jesus Loves Me."
"The Road to Sata is South."
"489239232."
"Super Duper."
"Pop goes 'Bang!' "
Pretty much anything that's really odd and short, should shut them up and preoccupy their minds with trying to figure out your mind. You'll also not have to tell them off verbally.
