Amid Evil
Very pretty fantasy FPS where the rocket launcher equivalent shoots planets (including earth) at dudes. Very fun, beautiful and has a soundtrack by Andrew Huschult.
AWOL
A free Build-engine FPS with a modern military setting. Very good, has vehicles that are pretty well done for a Build game and is also free.
Butcher's Creek
A first-person melee game by David Scyzmanski, aka the guy behind Dusk and Iron Lung. Kind of plays and feels like Condemned: Criminal Origins if it came out on the PS2 and OG Xbox.
Calcium Contract
Very fun classic FPS that has an aesthetic that reminds me of Pandemonium. Also has a neat twist on secrets and treasures, instead of hidden areas you have an enemy that carries the treasure chest that you must kill before it escapes the map.
Cavern of Dreams
Neat little platformer that feels like Spyro if it got made for the Nintendo 64.
Cry of Fear
Amazing survival horror FPS that is one of those few games to rival Silent Hill in terms of spookiness. It's also free.
Divine Frequency
Currently only has a demo on Steam, but holy crap does it hit hard. It's like Bloodborne meets Silent Hill, and it is terrifying AF.
Dusk
You probably already know this one. It's New Blood's flagship game aside from Ultrakill, and plays like it's own unique spin on boomer shooters with sliding and lots of acrobatic jumping and backflipping.
Fortune's Run
Amazing immersive sim platformer FPS thing that feels like MGS meets Shadow Warrior with an aesthetic reminiscent of Star Wars and an awesome soundtrack. It's only in Early Access, but I highly recommend it.
The Forever Winter
An indie game that has the graphical fidelity of a top-tier AAA game and an awesome setting that is a cyberpunk dystopia taken to WH40K levels of grimdarkness. Plays like a mix of MGS and DayZ.
Ghostware: Arena of the Dead
Cyberpunk themed FPS which plays like Quake III with sliding, has an aesthetic that reminds me quite a bit of TimeSplitters and has some Hypnospace Outlaw-ish web browsing bits to it.
Holstin
An isometric survival horror game set in a rural Polish town overtaken by zombifying ooze. Very fun and atmospheric.
Hrot
A boomer shooter set in the communist Czechoslovakia in 1986. It's insane on every level, from the enemies to the weapons to the fact that it was made with Pascal. Really fun, too.
Hyperviolent
A survival horror FPS that feels like 28 Days Later in space. Pretty fun, and it's primary gimmick is dual-wielding.
Ion Fury
A Build-engine FPS that is absolutely amazing. It's gorgeous (I tripped when I saw that they had put in animated voxels for frigging light switches), and has a protagonist that is like a female Judge Dredd. Also tangentially related to Duke Nukem.
...and I ran out of images. There's still more though...
Lost In Vivo
A survival horror FPS that has a bit of that Silent Hill vibe to it. It's terrifying and filled with secret levels and such.
Lunacid
By the same developer as the above, it's a game that is like King's Field but not tedious and boring! Highly recommend it.
Nightmare of Decay
It's a first-person survival horror game that feels like Resident Evil meets Blood. Pretty fun.
No More Room In Hell
A free FPS game that is like realistic Left 4 Dead. It's also free; stay away from the sequel until they iron out the glitches.
Shadows of Doubt
A cyberpunk detective simulation game that is set in a procedurally-generated voxel cityscape. It's very fun, I highly reccomend it.
SYNTHETIK
An isometric bullet hell-looter-tactical shooter hybrid which surprises me with how well they melded those genres together. Very fun.
Teleglitch: Die More Edition
An isometric survival horror game with a very crunchy retro aesthetic. Very fun, very difficult.
Viscerafest
A boomer shooter that is extremely difficult and insanely fun and rewarding. Highly reccomend it.