(Disclosure: This site contains product affiliate links. We may receive a commission if you make a purchase after clicking on one of these links. Read our affiliate disclosure for more info.)
GamersGate / GamersGate UK has Painkiller Hell & Damnation Collector’s Edition on sale for $7.49 / £6.24 (50% off) as the daily deal for 9/6/13.
Uses Steamworks.