My husband is a sonar tech aboard a fast attack submarine and during an underway (short trip out to sea) this past year, they pulled a prank on their senior chief. This particular chief was fond of using Velcro to put up announcements and the like up on the bulletin boards, so they 'kidnapped' the box of Velcro and hid it, and left a 2 page typed ransom note, complete with pictures of the box with a knife laying over it and their demands!
A boot camp prank he told me happened 2 days before graduation, at morning muster one of his fellow recruits wasn't in line. They found him-wrapped to his bed in lord only knows how many yards of dental floss . Once it was discovered who did it, the culprits were sent back to first week of boot camp, to repeat it!