Released this past August, Payday 2 and Lost Planet 3 are already about half off on Steam this weekend, as is Defiance, the MMO Syfy tie-in. Elsewhere, you'll find Far Cry 3 for $15 or $20 with a copy of Blood Dragon, last year's Assassin's Creed III for $12 at GamersGate, the Fallout franchise for 50% off at GameFly, an adventure sale at Green Man Gaming, and decent deals on BioShock Infinite and Call of Juarez: Gunslinger at Get Games. As a reminder, you have three days and change to take advantage of the Humble WB Bundle.

Steam
77 Payday 2 $17.99 (40% off)
69 Payday: The Heist $4.99 (75% off)
87 Antichamber $6.79 (66% off)
63 Defiance $4.99 (50% off)
57 Lost Planet 3 $24.99 (50% off)
61 Lost Planet 2 $4.99 (75% off)
69  Lost Planet: Extreme Condition Colonies Edition $4.99 (75% off)
87  Antichamber $6.79 (66% off -- today only)
Angry Video Game Nerd Adventures $7.49 (50% off)
Skull Girls $9.99 (33% off + free weekend)
Earth 2140 $2.49 (50% off)
Kerbel Space Program $16.19 (40% off)
Arena Wars 2 $1.99 (80% off)
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Amazon Digital
88 Far Cry 3 $14.99 (50% off)
81 Far Cry 3 + Blood Dragon $19.99 (56% off)
PixelJunk Bundle $16.89 (42% off)
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GameStop
86 Warhammer 40k: Dawn of War II $4.99 (75% off)
75 Warhammer 40k: Space Marine $7.49 (75% off)
60 StarDrive $10.19 (66% off)
X3 - Gold $12.49 (50% off)
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GamersGate
81 Overlord Complete Pack $4.99 (75% off)
87 Assassin's Creed III $11.98 (60% off)
80  TrackMania 2 Valley $10.00 (50% off)
TrackMania 2 Stadium $5.00 (58% off)
Legacy of Kain Collection $6.25 (75% off)
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GameFly
88 Fallout 3 GotY $9.99 (50% off)
Fallout New Vegas Ultimate Edition $9.99 (50% off)
80 King's Bounty Platinum Edition $24.99 (50% off)
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Green Man Gaming
83 Tales of Monkey Island $8.74 (75% off)
76  Wallace and Gromits: Grand Adventures $4.99 (75% off)
75% off Sam & Max titles
20% off select titles via "GMG20-ODON7-FLUA7"
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Get Games
Far Cry 3: Blood Dragon $6.29 (58% off)
91 BioShock Infinite $13.59 (66% off)
76 Call of Juarez: Gunslinger $6.29 (58% off)
68 Kane & Lynch 2: Dog Days $2.49 (75% off)
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GOG
75% off assorted Mac-friendly titles