Don't forget this Gem from MERP Critical fumble table (Rolemaster)
That would be a great way to kill dinosaurs.
Pull the worst move ever seen, and while the dinosaur is stunned from laughing for 3 rounds, the rest of the party can butcher it in safety.
Any well thought out fumble chart makes the following considerations:
1) Skilled combatants are less likely to fumble than unskilled ones, and ideally this is true even if the skilled combatant attacks more often than the unskilled one.
2) Fumble results don't make unnecessary assumptions about the combat situation, so that any result applies equally well to any situation. Fumbles generally shouldn't result in combat advantage of some sort.
3) Fumble results are significant enough to justify the bother of rolling for them, but not so significant that they usually determine the outcome of battles (and in particular the outcome of battles between skilled combatants). The same should also be true of criticals.
4) The fumble results are cinematic in that from the fumble result it's easy to imagine in a visual manner what has happened and to describe the scene with evocative and visually compelling language.
So long as the table conforms to those basic principles, I'm likely to be ok with it. I'm not really a fan of either criticals or fumbles, because in my experience they are so rarely well thought out and because on the whole they tend to favor NPC's more than PC's.