Steam is well-known for doing free to play weekends, often offering entire catalogs for free to users in an attempt to woo them in to buying. For the weekend of October the 16th, Valve has chosen Grey Goo, a tactical macro based RTS game, and Chivalry A first person mêlée combat game. Both of these games also receive a steep discount of 50% should you wish to buy them.
Chivalry is a first person mêlée combat game featuring many swords and other medieval weapons. its is bit old having been released in 2012 but still has a healthy community for online play. This is a multiplayer only title. The game does suffer from a bit of fatigue as it is short on game modes, but if you like bashing people with swords this is your best choice. 20$ gets you the game and your pass to fight against the legions of other sword lovers online.
Grey Goo is a macro focused RTS. Originally created by the team behind the Command and Conquer franchise. Fans be warned this one got pretty negative reviews upon its release. Personally I loved the old school macro-focus of the game, with its emphasis on base building, and not twitchy unit movement in combat. The campaign has full voice acting, and lots and lots of cut scenes, and the story is compelling, with three separate playable races. I really this game is a steal at 20$