Inspired by some of the classics like Return to Castle Wolfenstein and DOOM, the free shooter Darkenstein 3D has released and it's a rip-roaring good time. Disclosure: their press team provided GamingOnLinux with a key.
No nazi trickery involved here, it's free to grab and keep on Steam. However, the developer did previously announce after teaming up with publisher MicroProse that they're going to be doing some DLC expansions but they promised they will "*not* be bite-sized and we will *not* nickel and dime you". A first smaller expansion will come first, with longer expansions to follow.
Like something out of John Wick only a bit more supernatural, you're on a mission to save your precious dog, snatched away by the evil Gestapo. Armed with nothing but your beard (okay, you do get weapons eventually), as the "Hobo Guy" you'll be firing and strafing like your own life depends on it. With some funny physics interactions letting you smash through things, along with plenty of bloody gore it's quite a highlight to run through.

Direct Link
The game seemed to work perfectly with Proton 9 on Desktop Linux (Kubuntu).
If you love oldschool shooters that are a little bit silly, you'll no doubt enjoy this one. The slow-mo special power with your "Homicidal Rant" where you get health bonuses per kill was a nice touch. Some really fun design went into this one overall, with interesting level layouts and it can be quite brutal.
Game Highlights:
- Fast, Old-School Gameplay - No cover, no aim assist, no handholding. Just movement, aim, and survival. Dodge bullets, strafe through firefights, and master the deadly rhythm of retro combat.
- A Story of Desperation (and a Dog) - Rescue your kidnapped companion, Gunther, while unraveling strange mysteries hidden inside enemy strongholds.
- 13 Handcrafted Levels - Castles, caves, valleys, and desert towns; each packed with secrets, keys, treasures, and escalating danger.
- Dynamic Rat Companion - Turn the battlefield into chaos with your vicious rat sidekick. Distract enemies, combo with grenades, and create absolute carnage.
- Explosive Physics & Gore - Enemies fly, gib, and ragdoll in spectacular firefights. Props shatter, debris scatters, and every bullet leaves a mark.
Seems if you're in Germany you're out of luck on trying to play it right now though.