I was on a production DB once, and ran SHOW FULL PROCESSLIST, and saw "delete from events" had been running for 4 seconds. I killed the query, and set up that processlist command to run ever 2 seconds. Sure enough, the delete kept reappearing shortly after I killed it. I wasn't on a laptop, but I knew the culprit was somewhere on my floor of the building, so I grabbed our HR woman who was walking by and told her to watch the query window, and if she saw delete, I showed her how to kill the process. Then I ran out and searched office to office until I found the culprit -

Our CTO thought he was on his local dev box, and was frustrated that "something" was keeping him from clearing out his testing DB.

Did I get a medal for that? No. Nobody wanted to talk about it ever again.