Now we're talking. Guacamelee! Super Turbo Championship Edition is going to be a nice freebie for Xbox One owners. That's coming up next month as a part of Microsoft's Games with Gold promotion, though last month's selection, Max: The Curse of Brotherhood, will remain available in July. (The other June title for Xbox One, Halo: Spartan Assault, will no longer be free.)
On the Xbox 360 side, there's Gotham City Imposters from July 1 - July 15, followed by another treat in BattleBlock Theater, which will be free beginning July 16. Definitely take the time to queue up the download for that, and keep in mind it's best played with a friend.
Xbox Live Games with Gold for July 2014 [Major Nelson]