With QuakeCon in full swing (this Thursday through Sunday), Steam has slashed a myriad of titles from id Software and Bethesda including Brink, Fallout 3 and New Vegas, Elder Scrolls III and IV, as well as all versions of Quake and Doom. Meanwhile, Origin cuts 50-75% off titles including Mirror's Edge and Battlefield: Bad Company 2, and Direct2Drive has launched its Bullseye Shooter Weekend with 40-60% off Crysis 2, Bulletstorm, Section 8: Prejudice, F.E.A.R. 3, and Borderlands GotY.

Steam
QuakeCon Pack 2011 $69.99 (86% off)
Brink $24.99 (50% off -- also free to play through Sunday)
Fallout: New Vegas $14.99 (25% off)
Fallout 3: GotY $22.49 (25% off)
Elder Scrolls Pack $14.99 (67% off)
Quake Collection $24.99 (25% off)
Commander Keen $3.74 (25% off)
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GamersGate
Darksiders $4.99 (75% off)
Dead Space 2 $14.98 (50% off)
Assassin's Creed 2 Digital Deluxe $9.98 (50% off)
Tropico 3 $5.98 (60% off)
Dungeons $15.98 (60% off)
Hitman: Blood Money $4.98 (50% off)
The Saboteur $10.18 (66% off)
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Impulse
Two Worlds II $24.99 (50% off)
THQ Ultimate Bundle $49.99 (50% off)
Empires and Dungeons 2: The Sultanate $7.47 (50% off)
The Guild 2 Collection $24.99 (50% off)
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Direct2Drive
Crysis 2 $29.95 (50% off)
Bulletstorm $11.95 (60% off)
Section 8: Prejudice $5.95 (60% off)
F.E.A.R. 3 $29.95 (40% off)
Borderlands GotY $11.95 (60% off)

Origin
Mercenaries 2: World in Flames $4.99 (50% off)
Need for Speed: Undercover $4.99 (50% off)
Burnout: Paradise Ultimate $4.99 (75% off)
Command & Conquer: Red Alert 3 $4.99 (75% off)
Command & Conquer 4: Tiberian Twilight $4.99 (75% off)
Mirror's Edge $4.99 (75% off)
Battlefield: Bad Company 2 $4.99 (75% off)
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Games for Windows
Trainz Simulator 12 $39.99 (20% off)

Good Old Games
40-50% off Heores of Might and Magic titles