@Viss looking- there is literally nothing more satisfying than the sound and feeling of the Doom shotgun, followed by the tinny roars of death when you nail something with said shotgun. It's a distilled endorphin rush without compare. To conclude, those are happy braincells, and this is how we grow zombie soldiers.

(Technically it was Quake soldiers that had their pleasure centres wired to go off when they killed, but close enough).