In the event that you haven't downloaded it yet, Dead Space is available for free through Origin. There's no word on how long it will be available so don't wait if you're interested. Elsewhere, Steam has Sanctum 2 for a buck and change, Far Cry 3 is $7.50 at Amazon, GameStop has cut half off Rocksmith 2014 and Assassin's Creed IV, while The Walking Dead with its DLC is $7.49 and Borderlands 2 is $9.98 at GamersGate. Also, the latest Android/PC Humble Bundle expires in four days.
Steam
{pf id:90654 size:small} Sanctum 2 $1.49 (90% off)
{pf id:94168 size:small} Divinity: Dragon Commander $13.59 (66% off)
{pf id:85037 size:small} Sniper Elite V2 $7.49 (75% off)
{pf id:85037 size:small} Sniper Elite Franchise Pack $9.99 (75% off)
{pf id:89038 size:small} Deponia Trilogy $16.31 (66% off)
{pf id:36271 size:small} Alice: Madness Returns $4.99 (75% off)
{pf id:93977 size:small} Spelunky $5.09 (66% off)
{pf id:96093 size:small} Journey of a Roach $2.99 (80% off)
{pf id:38319 size:small} Velvet Assassin $0.74 (85% off)
Worms Revolution $5.09 (66% off)
Daedalic Entertainment Bundle $49.99 (77% off)
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Amazon Digital
{pf id:87154 size:small} Rainbow Six Vegas 2 $2.50 (75% off)
{pf id:86886 size:small} Battlefield 2142 Deluxe Edition $0.99 (93% off)
{pf id:38243 size:small} Splinter Cell: Conviction $5.00 (75% off)
{pf id:86589 size:small} Far Cry 3 $7.50 (75% off)
{pf id:86961 size:small} Far Cry 2 $2.50 (75% off)
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GameStop
{pf id:95522 size:small} Rocksmith 2014 $29.99 (50% off)
{pf id:96405 size:small} Assassin's Creed IV Black Flag $29.99 (50% off)
{pf id:54210 size:small} Tropico 4: Collector's Bundle $9.99 (75% off)
Sine Mora $2.49 (75% off)
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GamersGate
{pf id:86592 size:small} Borderlands 2 $9.98 (50% off)
{pf id:88893 size:small} The Walking Dead Pack $7.49 (75% off)
{pf id:83614 size:small} Ghost Recon: Future Soldier $4.99 (75% off)
{pf id:1083 size:small} AI War Four Year Anniversary Edition $4.25 (75% off)
Poker Night 2 $1.25 (75% off)
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GameFly
{pf id:89056 size:small} Hotline Miami $4.99 (50% off)
Foul Play $3.75 (75% off)
20% off select titles via "APR20OFF"
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Green Man Gaming
{pf id:82880 size:small} Q.U.B.E. $2.49 (75% off)
{pf id:1119 size:small} Alien Breed Trilogy $5.74 (75% off)
Superfrong HD $2.49 (75% off)
Skull Girls $5.09 (66% off)
{pf id: size:small} 20% off select titles via "9NXY7B-749QGZ-QIM2NG"
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Get Games
{pf id:84729 size:small} Aliens Colonial Marines $4.99 (75% off)
{pf id:87556 size:small} The Cave $3.74 (75% off)
{pf id:3589 size:small} Red Faction Collection $14.99 (75% off)
{pf id:2754 size:small} Kane and Lynch 2: Dog Days $2.49 (75% off)
{pf id:85077 size:small} Binary Domain Collection $5.74 (75% off)
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GOG
60% off Atari and Kalypso titles