Sorry, let me specify a little bit. Snapping necks would have to be done only with high accuracy. Meaning you couldn't just go around taking zeds out one by one with ease. However, if you did have high accuracy in unarmed (which I honestly can't believe isn't a skill branch yet) this would be much easier. Also you would be putting yourself at high risk of scratch/bite in that range. Secondly, you are right about the knock down from a crouch attack. It would require a loss of strength, due to loss of full body motion. Although, I do think if you were to hit one behind the kneecap you would have a good chance to knock them down. Would breaking the neck of a zombie kill it or even paralyze it? I would guess that based on normal lore, you would end up with a chomping head that can't move its body? Does the zombie still need its nervous system to move? I think the one thing we can all agree on is that you need to destroy the brain to definitely kill a zombie. However, a chomping head attached to a immobile body would be an easy zombie to finish off. For the sake of the game. I think it should just kill them...