Captain Wayne - Vacation Desperation is an upcoming retro-styled completely over the top FPS, it looks awesome and a demo is now live.
One I missed that was shown off during THE MIX event earlier this year. The game as a whole just sounds completely nuts. The developers own explanation of it is just ridiculous too. As they explain: "The hot pink-wearing, fish-chomping, cigar-huffing Captain Wayne refuses to let anything stand between him and his gory conquest to rob and humiliate every rich asshole around the globe."
You're also missing an arm, chomped away by a legendary "Vampire Whale" and so you replaced it for a shotgun. Now you're marooned, with your ship stolen and so off you set "annihilating everyone responsible".

Direct Link
It's actually using GZDoom, so you can most likely get it running in the Linux version of GZDoom. Otherwise, Proton is an option to try if you love your retro-fuelled shooters.
Highlights:
- Witness an elaborately hand-drawn, action-packed epic inspired by the FPS greats!
- Make use of the many devastating weapons in Wayne’s arsenal and achieve maximum destruction!
- Explore dangerous locales through 8 humongous areas all across Orca Isle!
- HALF GAME, HALF CARTOON! Delight in the Captain’s depth-defying tale in CAMPAIGN MODE as you view tons of animated cutscenes exploring his adventure.
- Experience a high-octane soundtrack that emphasizes AGGRESSION and CHAOS!
- Go for the gold in our ENDLESS MODE–how long can you survive the onslaught?
The demo is live on Steam now.