Chariot, Bad Company 2 and Darksiders 2 are October's Games with Gold
From the Major Nelson Blog:
Coming up in October, Xbox Live Gold members can look forward to three new free games on Xbox One and Xbox 360. Chariot, the newest ID@Xbox game from Canadian developers Frima, will debut on Xbox One as a free download, replacing September Xbox One Games with Gold title Super Time Force (if you haven’t already downloaded it, now would be a good time).
Then on October 16th, Xbox Live Gold Members can download Darksiders II (normally US $49.99) for free through October 31st.
*Titles are available as free downloads for qualifying Xbox Live Gold members in all markets where Xbox Live is available. Some regions may offer different titles depending on market availability.