Origin is running a limited time offer in which, if you download and install Battlefield 4 before August 14, you get to play the game for free for an entire week. Battlefield 4 is being offered for free on a time trial basis under the company's new Game Time program.
Previously, Titalfall was available for free for a full 48-hours. At present, Wing Commander 3 is also being offered by Origin. Download the same on or before September 2, and keep it in your games library forever, or as Origin likes to say it, "On the House."