I had a coworker who used to pick on me all the time. I believe he had a crush. One day I took an exploding pen to work. This pen had an explosive cap inside so when you pulled the cap off it would make a loud pow! That day I shook it at him and told him to behave himself and as I assumed, he grabbed the pen, and said "what is this, mascara?" when he opened it, it exploded. He about jumped out of his skin. There was no stopping it at that point, no one was off limits, even the boss. Lots of laughs that day!