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.
Cats are one of the more visible examples of mutants which didn't make the cut. In unmodified Clear Sky you can even see one in the "zoo" run by one of the Stalkers in the Duty base. They're a bit slower than Blind Dogs but harder hitting. They also tend to run in packs.
this model needs work, but all the other ones are neat