Dread Templar was great fun, and a very smooth experience. It even has melee weapons that aren't crap.

Wrath Aeon of Ruin was a mediocre experience for me. The shooting was fun, but there was a real lack of enemy diversity. I remember the checkpoints being funky somehow?

Og games like Quake, Doom and Unreal hold up really well. They can be modded to your hearts content too. Brutal Doom is just way too much fun

Blood is super fun, but unfairly difficult on the highest difficulty. It kicks your head in, until you learn, but every minute of the experience is fun. Until the maze-like levels and actual mazes make you dizzy.

Cultic is like a modern Blood, but an even more deliberate version. The demo is good fun and the game is cheap.

Poweslave Exhumed is something I remember enjoying as a kid. Iron Maiden themed romp through mummies. It kinda reminds me of...

Amid Evil and Hexen//Heretic. Both feature mystical weapons, mana for ammo and fantastical locations and monsters to kill. Amid Evil is a great shooter with survival modes, a full campaign and all Heretic and Hexen are older, more dated games that will hurt you. But I love them for it.

Dusk was rhe first new retro shooter I played, and it's fun. It's slick, has a nice deathmatch mode and the campaign doesn't overstay its welcome. I hear it has been surpassed by Hrot.

Blood West tricked me hard. It's not a boomer shooter, but more like a single player version of Hunt, or a wild-west monsterhunting Dishonoured? It's fun and unforgiving, but not a boomer shooter, even if it has guns.

EYE Divine Cybermancy could qualify, I guess. It's a trippy grimdark warhammer inspired rpg shooter. Very boomery in it's visuam style and lack of handholding, but definitely more modern than Quake.

Black Mesa is Half-Life, and it's good. Nuff said.

Haven't played enough of Hedon, Project Warlock, Ion Maiden, Incision, Prodeus, Graven or Rise of the Triad to say more than they exist.