Best one I've seen was a former manager of mine who was testing the performance of an API which was a descision tree underneath but insanely poorly implemented. He ran wrk against it and... Yeah, the rest you can imagine.
Mine was an unfortunate chain of events. Connecting to a databases was done through a specific server with port forwarging. A sysadmin changed the ports for whatever reason without notifying us so the port that was supposed to point to an alpha environment suddenly became production environment. We had done changes to an authentication system and the old wan was being depricated so I was going to get rid of it in the alpha environment. Soooo... Drop table sessions on production. Luckily that was an internal system so all that happened was that ~800 people got logged out.
Mine was an unfortunate chain of events. Connecting to a databases was done through a specific server with port forwarging. A sysadmin changed the ports for whatever reason without notifying us so the port that was supposed to point to an alpha environment suddenly became production environment. We had done changes to an authentication system and the old wan was being depricated so I was going to get rid of it in the alpha environment. Soooo... Drop table sessions on production. Luckily that was an internal system so all that happened was that ~800 people got logged out.