Void Bastards is my favorite action-roguelike, though not worth playing just for the dakka. It's the kind of game where you have to weigh the cost of the ammo and the risk of combat before deciding whether to fight at all. If you want something shootier, Enter the Gungeon is great too.

Serious Sam: The First Encounter (The Second Encounter)
POSTAL: Classic and Uncut
POSTAL 2

Here Sok

1st person perpective Shooters click here!

Can't go wrong with this as the gunplay still holds up after all these years and the original F.E.A.R has arguably the best AI in a shooter. I'd also recommend Unreal Tournament and Soldier of Fortune: Platinum edition, which are both guilty pleasures . The original xiii is fantastic as well.

Prodeus, Wolfenstein: The New Order, and Dusk are a few shooters that I like. And if you want to fire a chicken crossbow then there's redneck rampage.

Huh what's this?

Disregarding the obvious ones like Doom, Unreal, Deus Ex etc, I'd say Outlaws and IGI-2.
Outlaws for having a Wild West setting and glass cannon characters instead of the oh so tired hit point sponges of too many games. IGI-2 for being a poor man's Deus Ex with some excellent level design and one of the badassest sniper rifles.

XD ---- Nothing >:~)

IGI2 seems to have terribly broken mouse input, so it's a bit hard for me to recommend.

I enjoyed Ghost Recon a lot. If you're into realistic tactical shooters, give it a go.

Great suggestions.

Shameless plug to my topic:

https://www.gog.com/forum/general/recommendations_best_first_person_single_player_games_available_on_gogcom

There are great recommendations there which you might find interesting.

Let me also add Far Cry 2 to the recommendations. It is flawed, admittedly, but within its flaws is nothing short of a masterpiece.
Without even realizing I sank +150 h on it.

i've been playing dishonored a lot and id say it fits more of a fps criteria than a thief-like game to be completely honest. if you can't handle/don't like gore in games, try it, you get "rewarded" when you ghost through levels

Doom series is my favorite shooter atm. Not sure about GoG but it was on wistlist at least.