Smith and Winston from Execution Unit is some of the most fun I've had in a twin-stick shooter for some time, partly because I love blowing things up and Smith and Winston lets you do a whole lot of that.
War Brokers is a pretty good online FPS that has a number of different game modes like Battle Royale, Team Deathmatch and more. It also has vehicles and a lot of other surprising features.
Have you played Dandara? It's a 2d metroidvania platformer that's pretty unique, as you don't run along platforms like other similar games. Instead, you defy gravity by zipping from place to place and it's very interesting to play.
How about something a little different? Your Future Self is a somewhat short at 1-2 hours story-driven experimental text adventure and it's now supported on Linux.
I've had the pleasure of testing out the platformer DASH: Danger Action Speed Heroes for a while now and it's truly shaping up to be an impressive game.
One funding campaign I completely missed was Crossroads Inn, a fantasy tavern simulator that managed to get fully funded. It looks pretty good and it's coming to Linux.
SUPERHOT, a first-person shooter where time moves extremely slowly until you move, released originally way back in February 2016, just got a rather nice update for Linux gamers.
Good news vault hunters, the recently released free DLC for both Borderlands 2 and Borderlands: The Pre-Sequel adding in multiple graphical upgrades will be supported in the Linux version.
Flippfly (Race The Sun, Evergarden) have announced Cats Fly Helicopters, an amusing sounding game about being a cat flying around a simulated city full of physics and emergent gameplay. On the topic of Linux support, they had some comments for me when asked.