Basically 2 ideas, one more creative than the other..
Pretty simple and doesnt take alot of imagination. Find a way to rig thousands of set mousetraps on a ceiling or something, and release them as soon as the victim enters the room. I think it would be most effective in a warehouse or something big.
Well, we all know how the military drops tanks and such out of airplanes, well, what if there was a way to drop a purpose built room from an airplane? (With the SLEEPING victim inside) Of course, you dont want them to die, so strap parachutes or whatever to it.. But how insane would it be to wake up with no gravity??? This might be an over-the-top prank, but hey, Id do it!