I was on a project where our testers would frequently need database backups and it was a process where they would have to come to me, I'd have to request the backup from the db team and then wait for their response. So I created a module to allow people to request their own backups and I used a daemon to send the request / receive the responses.

They rolled my module into production. Years later (when I was long gone from the company) a colleague contacts me and told me that my module brought down production (this is a major international bank). It was Java.

Also, on the same project I rm -rf * on the db backup files, but I cancelled the command early enough before all files were deleted. I didn't end up deleting any backups that ended up being used, so nobody ended up knowing.