Passive aggressive passwords
When working at a financial institution in the 90's had a dick of a team leader, everyone hated him, had no management skills and wasn't a nice person.
So we done things like setting passwords for systems that run batch processing to things like <name>666 - even funnier when he had to use said password, he never said a word.
He got comeuppance though, he got a security guard fired for sleeping on the job, he was new and had a stinking cold and took a cold remedy that made him drowsy, the rest of us would've banged on the front desk and gone "WAKEY WAKEY!", not him, he went to the security lodge and reported him, tosser.
Anyway, he was now on the radar of security for "ratting on one of their own", overnight he used to vanish for periods of time, no-one could find him, especially when there was an incident, but security knew.
He was touring the dealers floors in the other building they had, turns out, he was stealing stuff he found, in one case, levered open a dealers desk to steal a psion 5, he went back the following night to get the rest of the bits and security stopped him on the way out at 3am with a "what you got there?"
During a parts audit, our inhouse engineers were found to be 30K short of spares before this happened.
Being a manager, he had been granted full access to the buildings to go anywhere.
From memory, they took him to court over the thefts.
Total dickhead he was and a thieving scrote as well.
Anon 'coz could still be identified who he is from my name.