Arrrrgh, Matey! Epic Games has the Skull and Bones (Open Beta, PC, Epic Games Store) available free to play from Feb 8 - Feb 11 (release day is Feb 16). Described as a co-op pirate, open world, action-RPG game. Here's the launch trailer. 

• In addition, there's a couple free to own games this week: Doki Doki Literature Club Plus and Lost Castle