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Machinarium is on sale for $2.49 / £1.87 (75% off) as the GamersGate / GamersGate UK daily deal for 5/17/13. This game is pretty cute and awesome. You can try out the web demo first.
Kingdoms of Amalur is 75% off as the daily deal for the EA Sale currently going on:
Kingdoms of Amalur: Reckoning Collection = $7.49
Kingdoms of Amalur: Reckoning = $5.99
Kingdoms of Amalur Reckoning The Teeth of Naros DLC = $4.98
Kingdoms of Amalur Reckoning The Legend of Dead Kel DLC = $4.98
The KoA titles require Origin.