While it wasn't an FPS, I used to dink around with a game called Foxhole.
I remember this one. I played it for about one weekend and joined some big server that had it map going for several hours if not days. Somehow my character was glitched and I became invincible. Then I proceeded to invade all the enemy encampments killing everyone in sight, stealing/destroying all their vehicles/items. I was the terminator, all gunfire at me seemed to do absolutely nothing. After an hour or so of this, most of the opposing team (who had a huge numbers advantage when I started) had logged out and I too logged out and subsequently uninstalled.
