I've found DCC's “mighty deeds” mechanic to be a very satisfying way to adjudicate called shots and the like. My only problem with it as written is that it's limited to warriors and dwarves. If someone else wants to attempt a called shot (and they always do, eventually!), you are pretty much put in a position where you have to say “no” (this is a bad thing), or you have to invent a whole new way to deal with it for these other character types. Instead, I propose to replace everyone's flat attack bonuses with (nearly) equivalent attack dice. This way everyone can perform crazy stunts – or at least try to. Note that warriors and dwarves are still the only classes that get to add their deed die rolls to damage. Everyone else applies it only to the to-hit roll. I've also excluded the use of the d5 and the d7 out of a simple personal distaste for those dice being used in anything that is rolled so often as an attack roll.
ALTERNATE CHARACTER ATTACK TABLE FOR DCC RPG AND OTHER FANTASY VIOLENCE SIMULATORS