A set of small, piecemeal mods for various aspects of S.T.A.L.K.E.R.: Clear Sky. Stash Auto-Filler, modifiable "Trophy" AK-47/2, cut content restoration (including cut monsters/mutants) and others, all available as individual packages for each change.
Ooo, "Immortal Zombie". Sounds bad, doesn't it? Believe it or not the Zombie was christened as such by the GSC devs. These guys take a hell of a beating before they go down... permanently anyway. Don't be surprised to see them drop like a stone only to get back up a few seconds later. And then do it again. And again. And again.