Back when I had a desktop, I usually had to shoo one of my 2 cats away from the top of the case all the time. The other one liked to rest on the top of my old monitor, but after I got a flat screen, that wasn't possible.
Now that I have a laptop, one of them likes to sit on my lap and attack the keyboard, since it has flashing lights. The other one just hangs around on a nearby chair, and will frequently come over and demand attention by jumping up on my lap and standing on my chest.