So, what other retro-style shooters should I check out?

[e11]

i've played Dusk, Cultic, Sprawl and Hedon.

EDIT: Recommended so far (and aren't just actual old shooters):

Amid Evil
Arthurian Legends
Ashes 2063
Blade of Agony
Boltgun
Chasm: The Rift
Chasmal Fear
Cultic
Devil Daggers
Divine Frequency
Echo Point Nova
Fallen Aces
Forgive Me Father 1/2
Gravelord
Gunfire Reborn
Hands of Necromancy
Hedon
Hrot
Ion Fury
Nightmare Reaper
Phobos (Doom3 mod)
Prodeus
Project Warlock
RealRTCW mod
Retchid
Severed Steel
Sprawl
Stife veteran edition
Supplice
System Shock.
Trepang 2
Turbo Overkill
Ultrakill
Wizordum
Ziggurat

[16 TIMES THE MIN REQUIREMENTS!!!]

Ion Fury.

[Nexxtic]

Ion Fury is a no-brainer.

The Last Exterminator isn't out yet, but I think that is going to be a big deal once it's out.

Forgive Me Father 2 launched out of Early Access a while ago and is also great!

[CarThief]

Hm, dunno if Prodeus counts, it's kinda retro-ish, or quake-ish. Besides that one and Ion Fury, not familiar with any other good recently made but retro-style shooters (not personally anyway, yet to play some of them).

If all else fails, the Build Engine games exist too, but as they're rather aged they might not live up to todays standards (Blood, Duke Nukem 3D, Shadow Warrior). There's also Doom 2, perhaps not as fun in today's age, but commonly used as a base platform for some pretty incredible mods out there on the ZDoom engine.

Or try some good standalone ZDoom projects like Blade of Agony on Realm667? (Though it's more of a tactical WW2 shooter, but still... And hey, it's free!)

[Phynrae]

Nightmare Reaper is definately worth a play.

[★C0pe★]

HROT

[Roamer]

Turbo Overkill, and the RealRTCW mod.

[597]

The free Doom mod Quake Champions: Doom Edition technically counts as "retro style", though its focus is the PvP so people who don't already love Arena FPS are unlikely to like it. I do consider it better than all the official Quake releases and think everyone should give it a shot, at least against bots for a bit.

[MantisTom]

Seconding Ion Fury. The sheer amount of content alone is worth it. Full length campaign of mostly well thought-out, quality maps. Then add the "Aftershock" DLC which (ymmv) added another 15 hours of gameplay along with new weapons etc. It will keep you busy AND having fun for months.
I've also had a lot of fun with Wizordum lately too. Very different vibe than the other "retro fps" games we usually love but the bright fantasy setting is a lot of fun for me. Definitely check it out a bit as it's not for all retro fps fans but I recommend it

[Peaberry]

I put tons of hours into HROT and Prodeus! Highly recommended.

[Innot]

Project Warlock, Hands of Necromancy, Supplice (early access), Stife veteran edition, Severed Steel (if you like Sprawl), Chasm: The Rift, Star Wars : Dark Forces, Turok, System Shock.

[getphobo]

Ashes 2063.

[nomansham]

Nobody's mentioned AMID EVIL. I thought it was great :(

[Terrortoma]

Amid Evil, Beyond Sunset, COVEN, CULTIC, Devilated, Diluvian Ultra, Diluvian Ultra: Awakening, Dimensional Slaughter, Dread Templar, DUSK, Ghostware: Arena of the Dead, Hedon: Bloodrite, HYPERVIOLENT, HROT, INCISION, Ion Fury, Nightmare Reaper, Postal: Brain Damaged, PowerSlave Exhumed, Prodeus, Project Warlock, REAVER, Relentless Frontier, Selaco, SPRAWL, STRAFE, Surplice, System Shock, Turbo Overkill, ULTRAKILL, Viscerafest, Warhammer 40,000: Boltgun, WRATH: Aeon of Ruin.

That's just a fraction of all the boomer shooters that I play.

And seemingly random caps because these kind of games are listed on Steam with their titles in all capital letters. :p

[Bruno Fisto]

Ashes 2063 and it's sequels.

[Ch33zyDischarg3]

I see a bunch of people recommending Prodeus. I politely disagree. It has excellent level design, visuals, and combat. But, the game makes you invincible. You die, and just re-spawn with everything as it was when you went down. Think of the bio-spheres from Bio-Shock. It takes away all challenge and sense of progression. For some people that might be fine, but if you're into boomer shooters (you like a challenge and hitting that save button), then it might be the best option.

Ion Fury, Cultic, Dusk, Amid Evil, Forgive me Father 1 and 2, Postal Brain Damaged, Boltgun, and HROT, are my favorites.