Valve

Valve is an American video game development and digital distribution company based in Bellevue, Washington, U.S.
They are well known for their first-person shooters and long development cycles, as well as extreme community support. They also created the Source engine, a mod-friendly engine, as well as having previous modders on staff.
==Games==
*Half-Life (1998 (PC), 2001(PS2))
*Counter-Strike (2000 (Retail) 2004(XBOX))
*Day of Defeat (2003 (Retail))
*Portal (2007 (PC))
*Left 4 Dead (2008 (PC, Xbox 360))