Well, on a critical hit I have a "colorful critical hit system" that adds some maiming and mutilation to a crit, based on the proportion of your hit points before the hit that are left after the hit. This means that you only take lethal critical effects (brain pierced, cut in two, decapitated, etc) if the crit actually kills you, and only nasty incapacitating crits if the crit incapacitates you (knocks you to 0 or below).
Some groups like fumbles, some don't. Mine has been begging me to redo and reinstitute my fumble chart for most of a year now; I just need to work out how to figure the severity. (I used a similar system for fumbles to that I use for crits, and for about 15 years, there's been a challenge- the first time anyone, pc or not, gets the "spontaneous human combustion" fumble, Craig is going to buy a keg of beer for all of us.)