by Tiertex Ltd., 1992
by Disney Interactive Victoria, 1998
by id Software, Inc., 1993
by id Software, Inc., 1994
by Sunstorm Interactive, Inc., 1997
by 3D Realms Entertainment, Inc., 1996
by Sunstorm Interactive, Inc., 2002
by In Utero, 2001
by Computer Artworks Ltd., 2000
by Rage Games Ltd., 1999
by Illusion Softworks, a.s., 2000
by Terminal Reality, Inc., 1995
by Argonaut Software Ltd., 1995
by 7th Level, Inc., 1997
by Monolith Productions, Inc., 1998
by Planet Moon Studios, 2000
by DMA Design Limited, 1997
by Rockstar Canada, 1999
by Valve Corporation, 1998
by Valve L.L.C., 2000
by Gearbox Software LLC, 1999
by Terminal Reality, Inc., 1996
by Raven Software Corporation, 1998
by Raven Software Corporation, 1997
by Raven Software Corporation, 1995
