I wrote a simple script once that ran in the background and all it did was toggle the state of the caps lock key every 30 minutes. I set it up on a co-worker's computer as a scheduled task for an April Fools prank one year. I thought for sure he'd figure it out pretty quickly, but by mid-day, he had completely disassembled his keyboard, convinced the button was getting stuck due to gunk buildup. Eventually I ended up just disabling the task so he thought he had managed to fix it himself.