Bullet penetration depending on the gun, fixing the torso from snapping when splitting open would be amazing. I'd love to be able to fire at a ragdoll until its torso is just pieces being held together.
I think bullets and other ballistic items should be able to take small chunks out of live items if possible. Maybe if an arm is moving upward fast enough, the bullet could go through it and hit the chest or other arm depending on how their moving. Both of these combined would be awesome as ragdolls would end up like swiss cheese.
A mutation power too, The mutation would kill from the main body first, if possible also could cause minor disfigurement in limbs (EG: shortness, distortion) would that be possible?
 "Mutilate-a-Doll 2"){kind=icon}