This is from my days of running a rather large (for its time) Minecraft server. A few of our best admins were given access to the server console. For extra security, we also had a second login stage in-game using a command (in case their accounts were compromised). We even had a fairly strict password strength policy.
But all of that was defeated by a slightly too stiff SHIFT key. See, in-game commands were typed in chat, prefixed with a slash -- SHIFT+7 on German-ish keyboards. And so, when logging in, one of our head admins didn't realize his SHIFT key didn't register and proudly broadcast to the server "[Admin] username: 7login hisPasswordHere".
This was immediately noticed by the owner of a 'rival' server who was trying to copy some cool thing that we had. He jumped onto the console that he found in an nmap scan a week prior (a scan that I detected and he denied), promoted himself to admin and proceeded to wreak havoc.
I got a call, 10-ish minutes later, that "everything was literally on fire". I immediately rolled everything back (half-hourly backups ftw) and killed the console just in case.
The best part was the Skype call with that admin that followed. I wasn't too angry, but I did want him to suffer a little, so I didn't immediately tell him that we had good backups. He thought he'd brought the downfall of our server. I'm pretty sure he cried.