Return to Vegas.
In July, a Xbox One debut title, 'The Banner Saga 2' (review here), will lead the Games with Gold offerings. 'The Banner Saga 2' will be free for the month of July for Xbox Live Gold members on the Xbox One, while from July 16th through August 15th, 'Tumblestone' will be free on the Xbox One for Gold members.
Of course, by way of backwards compatibility, there is more. For both the 360 and the Xbox One, 'Tom Clancy’s Rainbow Six Vegas 2' will be free for Gold members from July 1st through July 15th. For the second half of the month, 'Tron Evolution' will be the game.
Thanks to 'The Banner Saga 2' July looks to be a great month.
Source: Major Nelson