In Garry's Mod, a LOOONG time back (in GMod 9 I think), I logged on a server that said something like "lulz bild stuph" (but with better spelling). So, I got on it with the intention of building a contraption that I could show off, but when I got on everyone was DMing (randomly killing each other). So I said to myself "Oh well, might as well have some fun." So, I opened the spawn menu and noticed that the server was running Carmod. Excited, I spawned an SUV, changed my name to Soccer Mom, and started smashing into the random DMers. Next thing I knew, I was getting chewed out by the admin because I was running over them. I tried to retaliate, but seconds later I was banned.
I was also banned from my main multiplayer server on Freelancer because the lead admin was a jackass.