Saeviomagy
Adventurer
I think that there are games and plot setups that can work with "surprise, you need to go on a quest to fix bob!"
I also think that making a character completely non functional (petrified, permanently paralyzed, intellect devoured etc) is not the way to do this, because it removes the player from the game - they'd typically be better off if their character had permanently died so that they could just get on with it and roll a new one.
So - remove limbs, give crippling curses, reduce stats etc etc and make those conditions hard to fix, but don't totally eliminate the player from the game for an extended period of time while not allowing him to reroll.
I also think that making a character completely non functional (petrified, permanently paralyzed, intellect devoured etc) is not the way to do this, because it removes the player from the game - they'd typically be better off if their character had permanently died so that they could just get on with it and roll a new one.
So - remove limbs, give crippling curses, reduce stats etc etc and make those conditions hard to fix, but don't totally eliminate the player from the game for an extended period of time while not allowing him to reroll.