If you've been hesitant to invest in the latest version of Modern Warfare, Steam removes cash from the equation with a free multiplayer weekend (along with a 33% discount, if you enjoy the ride). Valve's distribution house also cuts 75% off 2009's sequel to Return to Castle Wolfenstein and 25% off some classic GTA titles. There are plenty of deals elsewhere, including Civilization V and Mafia II for $7.49 each, Borderlands for $4.99, as well as Human Revolution and Space Marine for $14.99 each.
Steam
{pf id:81834 size:small} Call of Duty: Modern Warfare 3 $40.19 (33% off + free weekend)
{pf id:38376 size:small} Wolfenstein $4.99 (75% off -- today only)
Grand Theft Auto 3 $7.49 (25% off)
Grand Theft Auto: Vice City $7.49 (25% off)
Grand Theft Auto: San Andreas $11.24 (25% off)
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GameStop
{pf id:37924 size:small} Sid Meier's Civilization V $7.49 (75% off)
{pf id:54185 size:small} Deus Ex: Human Revolution $14.99 (50% off)
{pf id:1452 size:small} Borderlands $4.99 (75% off)
{pf id:3437 size:small} Plants vs. Zombies $4.97 (50% off)
{pf id:2954 size:small} Mafia II $7.49 (75% off)
{pf id:1365 size:small} Bejeweled 3 $9.99 (50% off)
{pf id:38242 size:small} Rainbow Six: Vegas 2 $19.99 (50% off)
X-COM Pack $2.99 (75% off)
BioShock $4.99 (75% off)
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Amazon Daily Digital
{pf id:1343 size:small} Battlefield: Bad Company 2 $4.99 (75% off)
{pf id:2969 size:small} Magicka Collection $4.99 (75% off)
{pf id:1504 size:small} Burnout Paradise $4.99 (75% off)
{pf id:81453 size:small} Dungeon Defenders $2.99 (80% off)
{pf id:3004 size:small} Mass Effect $4.99 (75% off)
{pf id:3005 size:small} Mass Effect 2 $4.99 (75% off)
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GamersGate
D&D Neverwinter Nights Complete $10.18 (66% off)
Neverwinter Nights 2: Platinum $6.78 (66% off)
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GameFly
{pf id:80371 size:small} Warhammer 40,000: Space Marine $14.99 (50% off)
{pf id:1339 size:small} Battlefield 3 $44.99 (25% off)
Green Man Gaming
{pf id:54201 size:small} Saints Row: The Third $39.99 (20% off)
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Games for Windows
{pf id:2195 size:small} Fallout 3 $9.99 (50% off)
Good Old Games
50% off Age of Wonders
https://www.techspot.com/news/47498-weekend-game-deals-dungeon-defenders-3-wolfenstein-5.html