Sure, anyone can pull off the "salt in the sugar shaker" prank, but it takes true ingenuity to pull of something like this: a door-triggered air horn. Here come the heart attacks!
The supplies are minimal. Duct tape. Air horn. An inexhaustible capacity for sadism. Park this prank in your friend's bedroom/dorm/office, wait for the EEEEEEENHHHHHHHHHHHHHHHH and smile. [9Gag -- Thanks Nicko!]