If you're hacking away at skulls and the like (not the marshmallow skulls on TWD), you really do need quality steel.
I always thought that a good stabbing weapon would be a piece of tempered drill rod, ground down to a long, tapering point, and epoxied into a long handle. Sort of like an icepick on steroids.
You'd have to choose carefully so that you had one that would penetrate well without bending or snapping.