Final Fantasy XI, and then a patch comes that completely destroys the concept behind releasing your pet before a kill. You're tanking as a Frost Death Knight in World of Warcraft, and then you catch wind of the changes in 4.0. Your Invulnerable Tanker in City of Heroes is as untouchable as Superman, and then along comes a patch that coats everything in a light Kryptonite glaze.
You haven't just had your balance adjusted -- the entire way you play your character has been gutted and left lying on the ground as a warning to others. If you're lucky, you've never been on the receiving end, but the question remains: what do you do next? Do you start over with a different class? Leave the game gracefully (or less than gracefully, depending on temperment)? Or do you go with the approach that this is the class you came in with and you are sticking with it, by gum? As a bonus, have you experienced this firsthand, or are you lucky enough to have been spared?