this is simply the Item.xml that i changed to make headshots more effective.

Rough damage on insane difficulty:
Clubs need about 3-5 head hits to kill a zombie
Hunting knife about 2-3 head hits (sometimes more if unlucky)
Machette 1 hit kill to the head
Guns / Bow / Crossbow all 1 shot kill in the head.

some tools do increased damage as well :D
suchs as:
Pickaxes
Fireaxes
Boneshiv (this one still takes roughly 5-10 hits to kill)
auger and chainsaw pretty much have insta-kill on the head! (only the auger can be hard to aim at head!)

to install:
Simply drag and drop the ''items.xml'' into the folder!
Steam\steamapps\common\7 Days To Die\Data\Config

(this wont work with any other mods that replace the items.xml file!)

also, feel free to share this around! :)
but dont claim that you made it XD thats just a dick move ;P