Microsoft's Games with Gold lineup of free games for Xbox Live Gold subscribers in September is strong: Bungie's Halo: Reach, Capy Games' Super Time Force and Pocketwatch Games' Monaco: What's Yours Is Mine.
Xbox One owners get Super Time Force starting Sept. 1 via Games with Gold. Xbox 360 owners get Monaco on Sept. 1 followed by Halo: Reach on Sept. 16. Xbox Live Gold subscribers currently have access to download Crimson Dragon, Strike Suit Zero: Director's Cut and Dishonored at no charge until Aug. 31.
You can read Polygon's reviews of Super Time Force and Monaco for details on those upcoming freebies.