1) The hide and seek game... get his toy, throw it down the stairs, tell him to go get it. He wants to, because it's a toy and going and getting toys is the funnest thing in the world, but he knows that you're going to hide as soon as he runs down there, so he stands with two feet on the stairs and two feet on the floor and panics because he doesn't know what to do. Eventually he gets the toy and you hide and he runs back up and FREAKS because you're gone, and there aren't that many hiding places in our house, but it takes him a while to find us.
2) Downloading mp3s of squeeky noises. If you play them loud, then play them quiet, he thinks the noise moved into another room.
3) this isn't really screwing with him, but we let him sniff UPS packages that show up. It's like, his favorite thing, packages from THE OUTSIDE, so many new smells, I don't know.
4) going out the garage but not driving away. he looks out the front window to make sure your car leaves (how he grasps that concept is beyond me) and if he doesn't see it, he freaks out.
My roommate's out of town so I took him on a walk today, it was cute. Took a while to get his harness thingy on because he sees it and knows he's going on a walk and goes NUTS, so I literally had to put it back in the closet three times because he wouldn't calm down. And you can see him struggle with that whole thing... he's too excited to be calm, but also knows that he won't get the harness on unless he sits, so he sits and freaks out alternately, it's funny.