My cat likes to jump up on my lap when I'm on my computer. Sometimes, he will walk across my keyboard if he isn't getting the attention he thinks he deserves. I found the ultimate weapon! Compressed air, the kind you use to blow out your computer with. Cats hate to be shot with the air...now, all I have to do now is pick up the can, my cat gives me a go to hell look, and runs off to pester the birds or something.