Kleshik is a modification for ID Software's Quake1 FPS game. The goal of Kleshik is to augment the cooperative multiplayer gameplay with new features, along with update the game with modern effects, sounds, graphics and exaggerated feedback.
This and Darkplaces are the only reasons I still play Quake. It enchances the Quake dark horror feel with stingers and creepy ambience (Think F.E.A.R.) Fantastic mod-- it's too bad that it doesn;t get more recognition. Video of gameplay here: http://www.youtube.com/watch?v=vAlOllgH_uk