This might be a bit big, but the idea of limb/area based damage would be amazing. Sort of an extension of the @fatal command, but a lot bigger in scope. It'd still be possible to shoot wildly, not aiming at any one thing or another without specifically aiming for the legs or something, but it'd add so much. For example: Mixer A is carrying around a machete, swinging it around wildly because he's sky high. TERRA agent appears, and does "target mixer hand", so now, when he shoots, he'll automatically shoot for the hand. Someone gets shot in the hand, suddenly, they can't use it. Another situation would be if you were torturing someone, or being a sadistic fuck, you could just chop someone's legs off with a hatchet. Then they can't walk, and they have to dragg themselves along - They couldn't wear any pants or boots, and they couldn't drive cars. Mash someone's ear with a baseball bat, suddenly they can't have the auditory enhancements.
This leads into the second idea: Cybernetic limbs. Supposed you actually got your hand shot off because someone appreciates crippling you. You go to Westide or Fuller or whatever, and you get a metal hand installed. Suddenly, depending on how much money you spent on it, you either have a shoddy replacement for your former hand, or some sort of super thing that could also do Tattooing, or have a small derringer inside it. Cyber legs could be normal, or ostrich-like, or hell, a fuckin' arachnid if you wanted.
...Arachind legs sound awesome.