In the words of Microsoft, if you haven’t yet made the “jump” to the “next generation” of gaming with the Xbox One, well now is a better time than ever. If you buy an Xbox One at a participating retailer from September 7 through September 13, you will get a free Xbox one game of your choice. This offer is also valid for system bundles as well, but not refurbished consoles or used games.
*Offer valid September 7-September 13, 2014 at participating retailers with purchase of Xbox One, Xbox One with Kinect, Xbox One Madden NFL 15 bundle, or Xbox One Forza Motorsport 5 bundle. Free game must be a new, disc-based game for Xbox One, maximum retail value $59.99. Not valid for pre-order games. Limit one free game per eligible Xbox One purchase. Cannot be combined with other offers. Refurbished consoles or used games not included. See your local retailer for details.
Source: Official Xbox News