Hammer as a tool = device for banging nails in kept in a toolbox.
Hammer lovingly modded with extras and painted black, polished daily and practiced with daily. Kept on wooden rack in lounge and photos posted on various websites starting debate about minutiae of usage and semanics is no longer just a tool.
While not common with hammers, it is sufficiently common with knives and multitools. Want to get custom tools on your SAK or Leatherman? Want it Cerakoted? Want custom plier ends? Want a custom SAK blade? Want custom grips? Want custom pocket clips? There are people that do those things.
For the most part, a hammer is a hammer. As long as it is in decent shape, and is the right kind, any one will do as well as any other. Knives and multitools, however, are different enough from one another, in build/design, that two people may find themselves better off with different ones, even for the same work.
Much of the same can be said for lathes and routers, which people commonly customize and tweak, and yes, even show off, as much or more than, they use them.
A gun is a tool; but to be fair, it's much more akin to a folder, multitool, router, milling machine, lathe, etc., than a hammer, for doing a comparison of how one can become attached to one. It is a tool for the user, as much as it is for any specific task (usually the striking of far away bits of steel or paper ).