Stealth Inc: A Clone in the Dark, aka. Stealth Bastard: Tactical Espionage Arsehole, was a rather excellent murderous puzzle sneak ‘em up. It was a Windows freebie first, then an updated version was released on Steam, and so it was a little disappointing when the sequel turned out to be a Wii U exclusive (albeit providing further justification for my decision to buy one).
Prepare for stealth jubilation, however, because Curve Studios have confirmed that Stealth Inc 2 [official site] is coming to PC. Perhaps it was there all along, lurking in the shadows?