Want to pull a MAJOR prank on someone. Ideas requested.

[GretasGun]

My grandfather and great-uncle owned a beach house together back in the '60s. They used to play (harmless) pranks on each other, which drove the wives crazy, from what I remember. After vacating the beach house one weekend, my uncle set up a vacuum cleaner on a timer (like the ones used to turn the lights on and off) underneath the bed in the master bedroom, knowing that my grandfather would be there the next night. Well, the thing went off at 3am (so the story goes) and my grandfather woke up thinking that a freight train was running him over. Grandma didn't talk to my uncle (her brother) for three weeks.

Another funny (unsolved) prank that I had pulled on me:

The secretary at my work (75 people) was the big gossip in the office. She was responsible for opening all of the incoming mail and stamping the "Received" date stamp on whatever arrived. I get to work one morning to find a non-descript white envelope in my box (among other things), and think nothing of it. By the time I got around to opening the penis enlargement advertisement (which was of course stamped in), half of the office was chucking about it. Still haven't figured out who did it.