DUSK

I am prepared to make the bold and irresponsible claim that DUSK is so good that it's actually better than the id software classics it is trying (and succeeding) to imitate. And I love Doom to death.
It checks all the boxes: fast movement speed, lack of fall damage, intertwined and interesting maps (which are designed to be played with no starting weapons), plenty of secrets to find (none of which are timed, I think, unlike the ones in Doom!), and plenty of enemies to shoot with a variety of familiar weapons. On top of that, there are environmental objects that you can use in clever ways, though moving and manipulating them can be janky. And the game also plays with darkness in some levels, which I thought added to the atmosphere.
My only gripe with it is the music: it's good, but the intense battle action music kept playing when I had already killed all the enemies and was just exploring the map. It happened too often and got pretty annoying, so I had to disable it entirely.
I recommend playing on the second highest difficulty, Cero Miedo. The game will try to tell you that it's "not recommended for a first playthrough" -- ignore it, you'll be perfectly fine if you've played a video game before, and might even find it to be on the easy side. I do not recommend playing on the Duskmare difficulty, where you die from just one hit. Playing on Duskmare is tedious, especially if you're not savescumming, and requires you to become intimately familiar with the maps. That might not sound too bad, but you'll be forced to skip some of the sections and boss fights, and that's just not fun. Whichever difficulty you choose, absolutely do enable "intruder mode" -- that way, all the secrets you find will be much more rewarding and exciting.
Bonus fact: this game came out on same day/month that the original Doom did!

I'm late to the boomer shooter revolution, but I now see why Dusk is considered foundational in the genre. The short answer: the level design is brilliant. After playing through all three episodes, if I were to make a ranking of the most memorable FPS levels, Dusk would easily have several entries in the top ten. The experience is varied from claustrophobic corridors to combat arenas to wide open spaces. The environmental storytelling is top notch. As the game progresses, the aesthetics of the environments change significantly and in interesting ways. Just superb.
Secondly, and this is more a matter of taste, but I adore the horror-pastiche-as-theme vibe that Dusk exudes. I caught references to Texas Chainsaw Massacre, The Witch and H.P. Lovecraft. I'm sure there are many more references which went over my head.
However, it's not all sunshine and roses -- er, I mean, bloodstains and meathooks.
The weapons are... fine. Pistols, shotgun, super shotgun, assault rifle. You've seen all these before. There are no secondary fire modes beyond 'look down scope'. The most interesting weapons here are the shoot-through-walls crossbow and the sword which can charge and parry. The most fun weapon is the mortar launcher, whose rounds can be detonated mid-air with a secondary click.
The boss fights are merely perfunctory. You'll not find more here than a fat health bar and a mess of bullets to dodge. See 'Turbo Overkill' for a more recent entry which managed to do more to make boss fights interesting within the genre.
The final two levels of the game have a difficulty spike which seems a bit rough. A late difficulty spike is certainly not unheard of for shooters, and you can adjust the difficulty setting at any time, so not a big deal, but it did put a slight blemish on an otherwise flawless level progression for me.
Still, despite my criticisms, I absolutely recommend a playthrough. Dusk is worth it.

If the Discord server I am on didn't vote for Dusk as our monthly game, then I most likely would not have heard about it.
This game gave me old-school DOOM vibes, just with a scarier world and a way more horrifying enemy design. The weapons at our arsenal feel, sound, look, and play amazingly. Even with its old and pixelated graphics, Dusk manages to maintain an incredibly eerie mood throughout. The game's phenomenal soundtrack and sparse use of lighting contribute to an eerie atmosphere.
Dusk also has an HD-remastered version. Once you start the game on Steam, you get to pick between the original and HD versions. I have to admit that the original version was more pleasing to my eyes. I think it looks way better than the HD version of the game.
While playing the game, make sure to keep your eyes out for secrets and hidden places. There are some hilarious Easter eggs in the game. Without giving anything away, all I'm saying is baby faces!

Stone-cold instant classic. Pure, unadulterated fun from start to finish. Totally engrossing in its delivery of razor sharp shooting, 90s shooter aesthetic, and absolutely superb level design. Couldn't put this one down, it's an incredibly easy recommend especially on its current sale price.

Dusk isn't my favorite FPS, nor is it overwhelmingly out there.
It is simply very, very very good.
This sounds like a backhanded compliment, but it isn't. Play this game.

I literally pirated this game then bought it, it's THAT good. Looking forward to mod support.

Recipe for a perfect Throwback Shooter:
-take Quake as a base;
-mix it with Blood and Heretic (but filter out the hitscanners, they're like raisins and nobody likes those);
-pour a helping of Half Life;
-add the secret ingredients (it's love and fresh thinking);
-let it burn in the fires of Hell for about 10 minutes;
-sprinkle with a tinge of Painkiller.
DUSK is a retro-styled FPS created by a group of talented people as a love letter to the late '90s/early '00s shooter genre. It follows the Intruder (or DuskDude) as he shoots his way through three episodes of possessed hilbillies, demonic military personnel and worse while trying to uncover what started it all (and looking for treasure).
Right off the bat it's clear the visual representation is highly inspired by Quake, going so far as to deliberately make textures low-resolution and feature far fewer polygons than other games of today's age. There's even a pixellization level for those who want to feel like they're actually gaming on a 386. This doesn't stop the weapons from feeling threatening, nor does it stop the enemies from being rather impressive and in some cases downright scary. Additionally, unlike Quake, Dusk does not run away from having a wider range of colours present in its levels as well as subtle particle effects. The audio side especially is impressive, with weapon sounds feeling meaty and satisfying. This is also where the killer tunes of the soundtrack come in, grungy and rusty and dripping with atmospheric dread during the quiet moments before pumping you full of adrenaline for the bigger fights.
The gameplay is straightforward. You run around collecting weapons, ammo and health, and you're trying to get to the end of the level while plowing through all the enemy-shaped obstacles in your path. On the way you'll be required to find keys in order to open doors, and in the process may yet find secrets leading you to extra weapons, items and easter eggs. Sometimes there's also bosses to kill (or avoid, you can finish the entire game without killing a thing). The weapons available are standard FPS fare and you've seen all of them before, with maybe the exception of the Crossbow whose projectiles pierce all enemies and walls. It's all rather simple, and it doesn't need anything else because the level design compensates heavily. None of the levels took me more than 12 minutes, they're all intuitively built, impressive to behold and a blast to go through. On top of this, there are still some elements of gameplay reminiscent of Half Life or even immersive sims, where you can stack objects on top of each other to reach secrets or skip over areas, or where you're able to light campfires, pick up an enemy's guts, cook them over the campfire and devour them for a boost in health.
I'm not sure what else to say here. DUSK is the definition of short but sweet, built out of reverence for the 'good ol' days' yet infusing some New Age energy into the design. If you're a fan of high-octane frantic fragging DUSK is for you, and even if you're not, it's still very accessible for any kind of gamer. And if the singleplayer campaign did not tide you over, jump into Duskworld together with numerous other fraggers of all skill levels and shoot at each other while bunny-hopping like madmen and using the physics engine to your advantage.