So I thought about one very, very minor thing. I suppose it would be in some way inconvenient to add due to how the targeting system works, and just generally this is I bit dumb, but...
What about giving a player an ability to smack,or shoot already killed zombies or players? For example a player happened to kill your buddy? You wouldn't want to smash his head to submission, or perhaps to empty an entire clip of your pistol in the head of a villain? Or perhaps you got infuriated that a zombie bit you, and you wanted to smash his head in to pulp?
I mean, why not?