Plot: Zombie Driver is a vehicular combat PC video game. Set in a zombie apocalypse environment, a chemical accident/secret government project has turned the inhabitants of an entire city into shambling, aggressive opponents. Wikipedia
Plot: Pirates, Vikings and Knights II is a multiplayer team-based first-person action video game, developed as a total conversion modification on Valve proprietary Source engine. The game is currently in beta development stages, with its first public release on 1 January 2007. Wikipedia
Plot: Zombie Panic! Source is a cooperative survival-horror Half-Life 2 first-person shooter modification. It is the sequel to the Half-Life mod Zombie Panic. Set in the middle of a zombie apocalypse, players start as a small group of survivors attempting to stay alive. Wikipedia
Plot: Nuclear Dawn is a post-apocalyptic first-person shooter real-time strategy hybrid video game. It was originally announced in February 2006 as an amateur mod for the Source engine, but in April 2009 was revealed to have become a commercial project, still using Source, aimed at Windows PCs and Mac OS...
Plot: Half-Life 2: Capture The Flag is a multiplayer team-based capture the flag mod developed around Half-Life 2. The public beta version was released on February 23, 2005. The latest version of the mod was released to the public on December 8, 2011. Wikipedia