A good weapon that is actually in use these days for a similar purpose is a combat shovel. Its actually used by soldiers (or was atleast) to cut into a hostiles and can be used for decapitation or even just stabbing. It is also useful in the random necessities such as breaking a lock, digging a hole to plant crop, or just breaking down a barricade that was left by an unsuccessful survivor. It's traits are fairly well in consideration aswell, they are usually small (about arms length maybe smaller), they are sharpened at the edges of the metal head (basically like a sword), and they often have a pointed edge. Being that its a shovel in retrospect, I would imagine they would be fairly sturdy yet I think they would be hard to aquire and if you look into getting one a military surplus store would be your best bet.