Portal (2007), Buka Entertainment
Half-Life 2: Episode One (2006), Valve Corporation
Left 4 Dead 2 (2009), Valve Corporation
Final DOOM (1996), id Software, Inc.
Half-Life (1998), Sierra On-Line, Inc.
Half-Life 2: Episode Two (2007), Buka Entertainment
The Orange Box (2007), Valve Corporation
Left 4 Dead (2008), Valve Corporation
Half-Life: Opposing Force (1999), Sierra On-Line, Inc.
Half-Life (Game of the Year Edition) (1999), Sierra On-Line, Inc.
Half-Life: Blue Shift (2001), Sierra On-Line, Inc.
Counter-Strike: Source (2004), Valve Corporation
Half-Life (2001), Sierra On-Line, Inc.
Half-Life 2 (2004), Valve Corporation

Half-Life 2: Episode Two (2007), Buka Entertainment
Half-Life (1998), Sierra On-Line, Inc.
Final DOOM (1996), id Software, Inc.
Left 4 Dead 2 (2009), Valve Corporation
Half-Life 2: Episode One (2006), Valve Corporation
Half-Life: Opposing Force (1999), Sierra On-Line, Inc.
Half-Life (Game of the Year Edition) (1999), Sierra On-Line, Inc.
The Orange Box (2007), Valve Corporation
Left 4 Dead (2008), Valve Corporation
Half-Life 2 (2004), Valve Corporation
Half-Life (2001), Sierra On-Line, Inc.
Counter-Strike: Source (2004), Valve Corporation
Half-Life: Blue Shift (2001), Sierra On-Line, Inc.

Half-Life: Blue Shift (2001), Sierra On-Line, Inc.
Half-Life 2 (2004), Valve Corporation
Half-Life (2001), Sierra On-Line, Inc.
Half-Life 2: Episode One (2006), Valve Corporation
Final DOOM (1996), id Software, Inc.
Half-Life (1998), Sierra On-Line, Inc.
Half-Life 2: Episode Two (2007), Buka Entertainment
Half-Life: Opposing Force (1999), Sierra On-Line, Inc.

Half-Life 2 (2004), Valve Corporation
The Orange Box (2007), Valve Corporation
Portal (2007), Buka Entertainment

Half-Life 2: Episode Two (2007), Buka Entertainment
Half-Life 2: Episode One (2006), Valve Corporation

Left 4 Dead (2008), Valve Corporation
Left 4 Dead 2 (2009), Valve Corporation