Usually, Steam database is a good way to find leaks of unannounced games and ports from consoles to PC. This time, users have found some interesting names and info on the portal’s stats page:

Killing floor 2: unannounced game

Batman: Arkham Origins Blackgate HD:  this game, originally released on 3DS and PSVita, could have the same treatment as Castlevania LoS: Resurrection or Assassin’s Creed: Liberation.

Battleblock Theather: currently available in Xbox Live Arcade

Happy Wars: as Battleblock Theather, HW is only available in Xbox Live Arcade

Half Minute Hero Two:  this could be the sequel for western countries of Half Minute Hero. The game has already been released in Japan  under the name Hero 30 second.

30sechero Rumor:  Unannounced games found in steam database (Blackgate HD, Half Minute Hero Two, etc) | VGLeaks 2.0

The stats are not available anymore, so we can’t provide any screenshot. We will have to wait for the official announcements.

Thanks, Joystiq.