Last day of work at an old job, I put a couple of stink bombs under the wheels of the boss's chair. He sat down, rolled foward and heard a crunching going on. Half way across the office, you could her the OH! GOD! People started to pull out of the office. They ended up calling 911 for people being sick from the smell.
The police couldn't figure out what had happened. The boss had dropped his coffee cup and it broke, concealing the broken capsules. They figured it was a prank of some sort and had to have a cleaning crew come in and use an ozone machine and scrubbed down the office. Nice $3500 cleaning bill.
They never suspected me. THE FOOLS!!!!! Who says a lame trick like that can't bring tears to your victim's eyes and an evil grin across your face? Even years later.