Day 268 | However if you have a head filled with something other than a brain, like certain humans do, then the better Option is to just Crash them at the moon.
Lets not risk the bulldozer, those are insanly expensive.
A skull is not uniformly thick. You will not crush a skull with your fist but fractures are a real possibility depending on exactly where and how you strike.
Of course, if you want real combat effectiveness, forget about punching the skull and master the Sennen Goroshi instead.