Okay, here's one of my "off-color" pranks... At retreat, we all leave the room and head to the lodge for meals at the same time. One day at lunch, someone slipped out early, placed a "battery-operated marital aid" inside the storage compartment of someone else's sewing machine, turned it on, and slipped back out. When we all filed back to our machines, we heard the buzzing! The owner of the machine took it out and apparently had no idea what it was - the rest of us were on the floor, howling.