Unreal Tournament 2004, with few players it turns its normal frantic and fast paced gameplay into a suspensfull slower experience which is awesome.
I think you can get it on the internet archive as it stopped being sold on gog and steam this spring.
OpenRA - Do you remember the old classic series Command & Conquer ?
OpenRA takes the old original game, updates the controls to modern RTS controls, add new ai to play against, add support for modern resolutions and adds a good internet multiplayer system, all of this for free!