Paranoia

Paranoia (or Half-Life: Paranoia) — A single-player total conversion mod for the Half-Life game, was released on December 3, 2007 by a group of Russian enthusiasts. It has been released for both PC and the Sega Dreamcast (keep in mind this port is not official). The rendering of the modification uses OpenGL, which allowed for the use of modern visual effects such as bump mapping, reflections, detailed textures, 3D graphics, 3D skyboxes, and an improved model lighting system. The final version of the modification was released on April 9, 2008. The modification is based on the Half-Life (GoldSrc) engine and is distributed for free. After the release of version 1.1, the modification received a large number of positive reviews, and in January 2008, the ModDB portal named the Paranoia project the best single-player modification of 2007.

You play as a Russian officer part of the Spetsnaz. You are sent to the Udarnik Industrial Complex on a mission to eliminate the terrorist threats and protect the personnel. However, the game takes a darker turn when the player character (Major Kalashnikov) enters in the abandoned parts of the complex, revealing mutants and zombies alike. Nearing the end of the game, operatives from presumably the British military, reveal themselves. Earlier, it was revealed the terrorists were actually mercenaries, who were contracted by the British.