You have one weekend left to grab the Humble Jumbo Bundle 2, which offers $260 worth of games including Terraria, Orcs Must Die 2, the Age of Empires Legacy Bundle, Galactic Civilizations II: Ultimate Edition and more. Meanwhile, Steam has The Walking Dead: Season 2 for $9.99, Amazon is running an end of summer sale with Metro: Last Light Complete for $4.99 and Borderlands 2 for $6.66, GamersGate has Torchlight II for $5, Tomb Raider is $5 at Get Games, and Battlefield 4 is $13.39 at GameStop. 

Steam
77 The Walking Dead: Season 2 $9.99 (60% off)
71 Call of Duty: Ghosts Gold Edition $29.99 (50% off)
88 The Walking Dead $6.24 (75% off)
68 Halo: Spartan Assault $1.69 (66% off)
77  Killing Floor Bundle $12.49 (75% off)
Contagion $4.99 (75% off -- free weekend access)
Age of Empires Legacy Bundle $13.74 (75% off)
Grid Autosport $24.99 (50% off)
Rise of Nations: Extended Edition $9.99 (50% off)
Men of War: Assault Squad 2 $17.49 (50% off)
Dust: An Elysian Tail $2.99 (80% off)
50% off the Call of Duty franchise
More...

Amazon Digital
83  Metro: Last Light Complete $4.99 (75% off)
77 Total War: Rome II $20.29 (66% off)
82 NBA 2K14 $6.00 (80% off)
82 Battlefield 4 $14.99 (50% off)
87  Titanfall $20.00 (50% off)
87  Borderlands 2 $6.66 (67% off)
82  Napoleon: Total War $3.74 (75% off)
84  FIFA 14 $10.00 (50% off)
RollerCoaster Tycoon 3 $4.99 (75% off)
Batman Mega Bundle $22.46 (75% off)
C&C Utlimate Collection $5.00 (75% off)
Tony Hawk's Pro Skater HD $2.49 (75% off)
More...

GamersGate
86 Torchlight II $4.99 (75% off)
87 Borderlands 2 $6.80 (66% off)
85 Euro Truck Simulator 2 Gold $11.90 (66% off)
86 Dirt 3 $6.24 (75% off)
81 Grid $2.99 (80% off)
78 Grid 2 $7.50 (75% off)
68 Sniper Elite: Nazi Zombie Army 2 $7.50 (50% off)
61 Contrast $3.75 (75% off)
88 Total War Shogun 2 Collection $16.25 (75% off)
81 Overlord Complete Pack $2.99 (85% off)
88 Empire: Total War Collection $8.75 (75% off)
More...

GameFly
78 Tropico 4 Collectors Bundle $7.99 (80% off)
79 Metro 2033 $2.99 (80% off)
60 Darkout $4.99 (67% off)
77 Warlock II: The Exiled $14.99 (50% off)
70 The Lord of the Rings: War in the North $4.99 (75% off)
Kalypso Media Collection $49.99 (85% off)
More...

Green Man Gaming
Borderlands Franchise Pack $20.29 (71% off)
2K multibuy promo (3 games for $24, 4 for $28, 5 for $30)
90% off The Book of Unwritten Tales content
More...

Get Games
88  Tomb Raider $4.99 (75% off)
73  Surgeon Simulator 2013 $4.99 (50% off)
Dream $7.49 (50% off)
Stealth Bastard Deluxe $2.49 (75% off)
Hacker Evolution $2.49 (75% off)
Hacker Evolution Duality $4.99 (75% off)
More...

GameStop
67  SimCity $5.99 (80% off)
82  Battlefield 4 $13.39 (55% off)
85  Assassin's Creed IV Black Flag $11.99 (70% off)
88  Tomb Raider $4.99 (75% off)
80  Sleeping Dogs $5.99 (70% off)
86  Rocksmith 2014 Edition (No Cable Included) $14.99 (75% off)
79  Hitman: Absolution Pro Edition $6.99 (76% off)
More...

Origin
Wing Commander 3: Heart of the Tiger $0.00 (free)

GOG
60% off Activision titles