Toilet Troubles
My wife used to keep these little Godiva chocolates that she likes in her desk at work, but started noticing some of them missing and figured it must be someone from the overnight cleaning staff taking them. Fed up with losing her not-inexpensive treats, she decided to get revenge on the choco-thief in question.
My wife replaced the good chocolate with these little squares of chocolate laxatives that look just like real candies. The next morning, she saw several of the laxatives were gone. Mission accomplished. From that day forward, she was never missing another one of her good chocolates ever again. I imagine the toilet trouble was a lesson learned.
Story credit: Reddit / VictorBlimpmuscle