That is because you are uncreative, haven't thought it through and have 12" biceps

Lets assume its the tier 3 club for a minute. A hammer is a hammer, so no. Sorry but I've used hammers more than anyone on this forum with years of auto body pounding out dents, heat shrinking metal, bending frames, etc and then my venture in real estate where I restored over 20 houses, loads of hammer time here as well framing, roofing, etc. A framing hammer without the head isn't very heavy, not even close to having the thump you need. The handle is deliberately light on those, all the weight is IN the head where it hits the nail for maximum impact and leverage. Grind that down and you have a light weight metal stick.
A bat, yeah perfect but lets say they break, and they do. As a guy who breaks bats all day you are tired of it, and construct the ultimate zombie killing club, something heavy, with junk on the end to help tear flesh and put dents or holes in their head while you are swinging, rather than just a contusion. Some gears welded to a shaft, a wrap around hand guard to really secure the grip even if you get hit from behind and stunned your trust club doesn't fall out of your hand. Its perfect.