Halloween sale are creeping in with half off Metro: Last Light, Baldur's Gate: Enhanced Edition and a Modern Warfare bundle, as well as even larger discounts on the Batman: Arkham titles, Stardock releases, the Dirt franchise and various horror-themed games at Green Man Gaming. Additionally, the Humble Bundle folks are serving up a new set of Android-friendly titles, including The Bard's Tale and Worms Reloaded.

Steam
90 Batman: Arkham City GotY $7.50 (75% off)
90 Batman: Arkham Asylum GotY $5.00 (75% off)
78 Scribblenauts Unlimited $4.99 (75% off)
82 Chivalry: Medieval Warfare $6.24 (75% off + free weekend)
78 Fallen Enchantress $7.49 (75% off)
60 1C Racing Collection $4.99 (75% off)
78 Stardock Pack $22.49 (75% off)
MotoGP 13 $19.99 (50% off)
Galactic Civilizations Complete Pack $7.49 (75% off)
Jagged Alliance 2 Gold $4.99 (75% off)
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Amazon Digital
83 Modern Warfare Bundle $34.99 (56% off)
69 Cities XL Platinum $9.99 (67% off)
72 Blood Bowl: Chaos Edition $7.49 (75% off)
55 Game of Thrones $7.49 (75% off)
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GameStop
84 DMC - Devil May Cry $24.99 (50% off)
67 Star Trek $14.99 (50% off)
82 Lego Batman 2 $7.49 (75% off)
77 Lego Lord of the Rings $4.99 (75% off)
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GamersGate
79  Metro 2033 $3.74 (75% off)
83  Metro: Last Light $19.98 (50% off)
82  Euro Truck Simulator 2 $8.50 (66% off)
80  Baldur's Gate: Enhanced Edition $7.49 (50% off)
44  Stronghold 3 Gold $7.49 (75% off)
44  Stronghold Collection $4.99 (75% off)
Rollercoaster Tycoon Deluxe $3.00 (50% off)
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GameFly
80  Square Open World Bundle $12.49 (75% off)
80  King's Bounty Platinum Edition $24.99 (50% off)
71  The Saboteur + Mercenaries 2: World in Flames $4.99 (83% off)
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Green Man Gaming
67 Aliens vs Predator $3.74 (75% off)
77 The Darkness II $7.49 (75% off)
56 Lucius $4.99 (75% off)
86 BioShock Pack $9.99 (75% off)
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Get Games
87 Civilization V $7.49 (75% off)
85 Dirt 2 $3.74 (75% off)
86 Dirt 3 $6.24 (75% off)
71 Dirt Showdown $7.49 (75% off)
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GOG
60% off point-and-click titles