To celebrate 10 years of Assassin's Creed Ubisoft will give away Black Flag, which could be the second best game in the series (behind AC: Origins of course).
Although Assassin's Creed IV: Black Flag came out in 2013 the game still holds up tremendously well today, and deserves a spin. Ubisoft will give away free PC copies of the game starting December 12, but you'll only have a limited window of opportunity to register and receive the game. Of course this promo is available on uPlay, the company's proprietary storefront/game service. Signing up for uPlay is worth it to get this one, though: Black Flag is a fun romp through the Golden Age of Piracy and takes you across the Caribbean as you wreak total havoc, pillage, and sink ships.
Right now Ubisoft is giving away the World of Conflict Complete Edition for free on uPlay, so grab that if you want something to play right now.