A fluke on the Steam stats page may have revealed several unannounced games, several users on NeoGAF report.
NeoGAF posters, including “jshackles,” were able to snag screenshots of the Steam & Game Stats page, which typically tracks the most-played games by player count, instead showing what appears to be developer build stats for games yet to be released on Steam, such as Murdered: Soul Suspect, BattleBlock Theater, Incognita, and Dead Island: Epidemic. In addition, the list revealed several unannounced titles, including Half-Minute Hero Two, Killing Floor 2, and Batman: Arkham Origins Blackgate HD.
Because none of these titles are confirmed, this report is to be, at best, regarded as a rumor. But because the list contains so many titles we do know are coming to PC and Steam, I’m very much inclined to believe the veracity of its contents. The full listing and several screenshots of the same list can be found on the NeoGAF gaming forums.