Most of the time the free games are a bit "meh!" but December has Burnout Paradise on BC! :-O I loved that game on my 360 so I'm hyped about being able to play it again and with my lovely new XB1S it should upscale lovely to 4k! Cannot wait.
The rest of the games are :
On Xbox One, Xbox Live Gold members can download Sleeping Dogs: Definitive Edition ($29.99 ERP) for free during the month of December. Outlast ($19.99 ERP) will be available as a free download from December 16th to January 15th.
On Xbox 360, starting Thursday, December 1st, Outland ($9.99 ERP) will be free for Xbox Live Gold members through December 15th. Then on December 16th, Xbox Live Gold Members can download Burnout Paradise ($14.99 ERP) for free through December 31st.