Worked somewhere where they had specialist keyboards for the software packages they used. One day I get a call from one user saying that the software is kaput as it doesn't respond to some keyboard commands. There had been an update to the software recently but I thought it odd that only one user was affected. Visiting his desk I realised that this bloke was a bit of a slob, there were wrappers everywhere. The specialist keyboard had large 5cmx5cm keys instead of regular keys but was actually just outputting the certain key combinations usually involving the control key. He demonstrated that the software wasn't working by pressing three of the keys and nothing happened.
The company charged a bit for these things and so it sucked that one had failed. So I plugged in a regular keyboard and tried the troubled key combinations which worked fine. I put in a replacement specialist keyboard and took the other one back to investigate. Upon opening the keyboard up I discovered that there was a wooden lollypop stick that had some how gotten in underneath the keys. The three keys that didn't work had that sticky wood preventing the keys from working. Weirdly he must have done something special to get it under there as we couldn't replicate what he'd done.