I'm definitely not a fan of "you screwed up and impaled yourself" and I wouldn't play any game that worked that way. The way we do it is that you have to confirm fumbles just like criticals, except in reverse... if you roll a 1 to hit, you roll again, and if you miss again, you provoke an attack of opportunity (from anyone who threatens you, of course).
That's all. You'd be surprised at how much this *doesn't* screw the PCs. Against peons, confirmed fumbles are rare, because they're usually relatively easy to hit, and even if you do provoke an attack of opportunity, the opponent often misses (or has already used his attack of opportunity). On the other hand, PCs often pound the crap out of monsters who fumble... I've actually seen, on several occasions, a monster die because someone provoked an attack of opportunity and it fumbled the roll, and the PCs housed on it.
I like it... it happens just enough to give combat a little extra randomness in the negative direction to counteract the randomness of critical hits, and it takes almost zero extra time.
While fumble charts like the one Scharlata posted are fun to make and fun to look at, but I would hate playing with them. Your 200000 gp weapon can spontaneously fall apart? You could critically hit a teammate? Those are hugely bad things that could sway a battle drammatically, or even change the course of a campaign!
And by the way... Loose is the opposite of tight. The word you want is lose. You lose money at a casino.
-The Souljourner