Yes pick up the critical fumble deckBecause nothing is more fun than cutting your own head off in melee
Pretty sure that card doesn't exist. I think there's one where you cut off a hand, but it's yet to come up in my games.
One rule variant (all fumble rules are rule variants) allows for anyone with Weapon Focus to draw two cards and pick between the two effects, which is one way for melee-characters not to be so bad off as everyone complains that they are with fumbles in the game.
The last fumble card that came up in my game saw a burning skeleton get his claw stuck on his skull and accidentally destroy himself. Card effect was that he inflicted his normal attack damage to himself. He was immune to his fire damage, but claw attacks deal slashing AND bludgeoning damage so he bypassed his DR/bludgeoning and it was enough to destroy him. Then, because he was a burning skeleton, he also exploded.
I specifically had the burning skeleton drop his two-handed weapon to use two claw attacks, and it was the second claw attack that did him in. (First was just a miss.) He didn't even stay in combat long enough for the party to suffer from his burning aura at the start of their turns.
Hopefully the martial characters in my campaign will take Weapon Focus sooner rather than later. Hmm. I should probably give more of the bosses weapon focus too. The main melee boss has weapon focus (greatsword) and weapon focus (slam), but not because I was thinking about the Critical Fumbles. He just had feat slots that I couldn't decide how to fill.
Anyway, TL;DR version is that Critical Fumbles are a variant rule, and not all variants are equal or terrible.