Half-Life 3 still hasn't seen an official announcement, but the long-awaited game from Valve might be closer than you think. As discovered through the Office for Harmonization in the Internal Market, which deals with the European Union's trademark filings, Valve recently trademarked "Half-Life 3" in Europe, fueling speculation about the game.
The trademark was filed on September 26, and covers "computer game software", "downloadable computer game software via a global computer network and wireless devices" as well as other good and services. While the trademark was discovered in Europe, searching through the US Patent and Trademark Office doesn't reveal an equivalent trademark for the United States.
The most recent entry in the Half-Life series was released in 2007 as Half-Life 2: Episode Two. Since then, fans of the series have been holding on to slim rumors and information relating to Episode Three, which was announced in 2006 but subsequently failed to materialize. There's speculation that a full sequel - Half-Life 3 - is in development, but Valve has yet to make any official reveal.
Valve's most recent line of announcements have surrounded bringing Steam into the living room. The first revealed SteamOS, a Linux-based OS designed for Steam; the second was Steam Machines, specific PC gaming hardware for SteamOS; and the third unveiled the Steam Controller. Rounding off the announcements with Half-Life 3 would certainly please a lot of gamers, but for now, the title will remain one of the most elusive in recent times.