If you've yet to try 2016's Hitman reboot, now could be a good time to dive in. The game's first proper chapter, set in Paris, is currently free on PS4, Xbox One, and PC. In addition, developer IO has announced the game's Christmas-themed missions are going free of charge for a limited time.
The game's introduction has been free since June, but Paris marks Hitman's first fully-fledged portion, and it's a great example of what the game offers. This free version of the level includes everything you'd get if you'd paid for it, and it's free from now until January 5--though if you download it now, it will remain free for you after that date.
Hitman's Holiday Pack is also available for nothing right now after being introduced this time last year. It includes two thieves attempting to ruin Christmas by stealing everyone's presents, and it also lets you throw a brick at Santa (don't try this at home).
Link to steam here.