We already know one of the titles heading to Xbox Free Play Days this weekend, as Ubisoft has confirmed that Far Cry 6 will be getting a free access period from Thursday to Sunday, with pre-installs available now.
You'll be able to play the full version of Far Cry 6 for free from February 16th at 4PM local time until February 20th at 4PM local time, and any progression you make will transfer over if you decide to buy the game in the future.
Far Cry 6's free weekend is available across Xbox One, Xbox Series X and Xbox Series S (along with various other platforms), and you can pre-install it by heading to the Far Cry 6 Xbox Store page and hitting "Get Free Trial".
You probably do want to do that as soon as possible as well, as you're looking at around 100GB worth of content here, so anyone with a slow connection could be waiting many hours for this one to finish downloading...