Half Life 3 may not necessarily be confirmed, but changes in the way that SteamDB was able to track package additions have confirmed a number of games that were previously hidden from the public. In short, Steam automated the ability to remove games from your Steam library not too long ago, and thus, people have been scraping the data from that function to find quite the hefty list of unannounced titles. They are:

• Everybody's Gone to the Rapture
• Criminal Girls
• Danganronpa 1 + 2
• Steins;Gate
• Final Fantasy X/X-2 HD
• Guilty Gear Xrd -Sign-
• Earth Defense Force 4.1
• Stranger of Sword City
• Bad Rats Show
• Half Life 3
• Space Pirates VR
• Arslan Musou
• Phantom Brave
• Ray Gigant
• Code of Princess
• Xblaze: Code Embryo
• Final Fantasy VI

The SteamDB team does go on to say that it's entirely possible that any of these titles may have been scrapped some time ago, and are no longer in development. As is such, SteamDB has an entry for Halo 3 that has seen nothing come of it yet. None of these entries are false, per se, because they have to exist within the database to show up here, but it does not mean we'll hear anything about them any time soon. Of course, some of the entries have been rumored for a while, such as Xrd Sign or Bad Rats Show, but it will be interesting to see what, if anything comes of this news in the future.