With Halloween around the corner, many outfits are celebrating with savings on horror titles, including 75% off Left 4 Dead 2 and Killing Floor at Steam (the former of which is also free to play this weekend), as well as 40-75% off The Walking Dead, both Dead Space titles, a F.E.A.R. Bundle and Dark Souls at GameStop. Elsewhere, you'll find half off Alan Wake, The Chronicles of Riddick and Legend of Grimrock at GOG, 75% off Rayman Origins and Super Meat Boy at Get Games, discounted THQ titles at GameFly and a war-themed sale at Green Man Gaming. It's not included on the list, but it's also worth noting that G2Play offers a Far Cry 3 preorder for only $32.26.

Steam
88 Left 4 Dead 2 $4.99 (75% off -- free weekend)
77 Killing Floor $4.99 (75% off)
77 Rock of Ages $2.49 (75% off -- free weekend)
Trains vs Zombies 2 $8.99 (50% off)
Dungeonbowl $7.49 (50% off)
Metal Drift $2.49 (75% off -- today only)
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Amazon Digital
86 BioShock Dual Pack $7.49 (81% off)
68 Need for Speed: The Run $4.99 (75% off)
86 Need for Speed: Hot Pursuit $4.99 (75% off)
87 Burning Hot Bundle $7.99 (80% off)
87 L.A. Noire Complete Edition $11.99 (60% off)
78 Tropico 4 $19.99 (50% off)
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GameStop
81 The Walking Dead $14.99 (40% off)
85 Amnesia: The Dark Descent $4.99 (75% off)
74 Dead Island GotY $9.99 (50% off)
87  Dead Space $4.99 (75% off)
89 Dead Space 2 $4.99 (75% off)
79 Metro 2033 $4.99 (75% off)
71 Alice: Madness Returns $4.99 (75% off)
82 Call of Duty: Black Ops $19.99 (50% off)
72 F.E.A.R. Bundle $14.99 (50% off)
77 The Darkness II $10.19 (66% off)
69 Risen 2: Dark Waters $24.99 (50% off)
51 Resident Evil: Operation Raccoon City $24.99 (50% off)
47 Painkiller Bundle $7.49 (75% off)
74 Dark Fall: Lost Souls $4.99 (50% off)
78 Darksiders II $24.99 (50% off)
83 Alan Wake $14.99 (50% off)
Fort Zombie $2.49 (75% off)
Ghost Busters $4.99 (50% off)
Vampire: The Masquerade - Bloodlines $9.99 (50% off)
Dark Souls: Prepare to Die Edition $26.76 (33% off)
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GameFly
78  Darksiders II $24.99 (50% off)
83  Saints Row: The Third $13.59 (66% off)
75 Warhammer 40k: Space Marine $7.49 (75% off)
86 Warhammer 40k: Dawn of War II $7.49 (75% off)
71 Red Faction: Armageddon $4.99 (75% off)
70  Homefront $4.99 (75% off)
58 Gemini Wars $19.99 (50% off)
Nexuiz $2.99 (70% off)
Titan Quest $3.75 (75% off)
Company of Heroes Gold $7.49 (75% off)
S.T.A..L.K.E.R.: Shadow of Chernobyl $4.99 (75% off)
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Get Games
88 Rayman Origins $7.49 (75% off)
76  From Dust $3.74 (75% off)
85 Super Meat Boy $3.49 (75% off)
83 Worms Reloaded $9.99 (50% off)
Worms Crazy Golf $4.99 (50% off)
Rayman Raving Rabbids $2.49 (75% off)
Gods vs. Humans $4.99 (75% off)
Eufloria $4.49 (75% off)
Dreamcast Collection $7.49 (75% off)
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GOG
83 Alan Wake $14.99 (50% off)
80 The Chronicles of Riddick: Assault on Dark Athena $7.49 (50% off)
86 Legend of Grimrock $7.49 (50% off)
80 Trine $4.99 (50% off)
30-40% off Deponia titles
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GamersGate
55  A Game of Thrones: Genesis $13.59 (66% off)
Pacific Pack $4.50 (90% off)
60-75% off Settlers titles
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Green Man Gaming
Up to 75% off war-themed titles including Red Orchestra 2 and Ghost Recon: Future Soldier