The trademark filings (documented here and here, though public viewing requires a unique search session) specifically mention Agent's distinct logo, which features "the shape of a handgun comprising the internal section of the letter 'G'". No additional details regarding the project's current status are yet known.
Announced as a PlayStation 3 exclusive in 2009, Agent is a stealth-action game with a storyline set during the Cold War in the 1970s. The game later slipped to a 2010 release date, but failed to materialize.
Rockstar announced in 2011 that Agent was "still in development," but has not issued a clarifying statement in the years since.