I'm perfectly fine with kicking knees (stomp-kick, not ballet-pointy-toe kick), kicking ribs hard enough to do some damage once they're down, stomping on a throat, and doing some serious injury to Junior and the Twins. Then I would get really serious and bash their head in.
That sounds like the fight scene in the kitchen at the
Guest House Paradiso 
+1 on Susan's brand of aggression against an attacker.
Cracking knees is not for the squeamish though, if you're making a plan to disable an attacker I suggest some practice, and make sure you will carry it out if the time comes: I have seen a self-defense school simulate an effective knee kick with a wood 'leg-knee' stuffed inside a pair of pants, they stand up the dummy and they take turns kicking the knee out. Think too about disarming your assailant - following the knee kick you still have to take away their weapon, don't rely on them dropping it or being so distracted that they wouldn't still shoot you.
So make a plan, visualize it all the way through disarming your attacker, and consider running through the scenario and your response (sudden / surprise aggression) in an evening at least at a self-defense class, which should be in your area somewhere.
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