What are some good cooperative shooters? Hidden gems?

The dying light games are great coop

Ghost Recon: Wildlands
Really fun to coop in either players' world to just line up shots and generally wreak havoc.
- Fuuuucking this.
  It's Grand Theft Auto; Special Forces.
  I wish they didn't absolutely butcher the sequel. It feels fucking awful compared to Wildlands.
  
  Yeah I loved Wildlands but couldn't get into Breakpoint. Glad I'm not alone, at least.
- And it's on sale for 10$ on steam rn, damn. It's missing the multi-player tag, otherwise I would have had it on my wishlist for co-op 3rd person shooters sooner :<

I second deep rock galactic
- Rock and stone!
  
  For Karl!
- Thirded.
  Also, is your username a cosmere reference?
  
  yes it is. Stormlight archives is my favorite series.
- WE'RE RICH

Deep Rock Galactic and Helldivers 2 are the ones I play. Usually at 2 players.
- Helldivers 2 is pretty good. Surprisingly not toxic/salty for how big it is.
  
  I take it you've never had the displeasure of being dropped into a PlayStation lobby? Lots of TKers and Kickers on PS. I don't get the same from Steam players.
  
  In-game everyone is usually wonderful.
  The official discord server, on the other hand... no. Just no.

Killing floor 1/2, fps zombie horde killing.
Another doot for Remnant, really enjoyed the odd universe and two player coop.
Battlefront 2 multi player for mindless star wars pew pew fun.
- You recommended killing floor before L4D2? Interesting.
  
  Hasn't someone already suggested L4D2? I only played the first and was pretty offended when they promptly released the second and expected me to pay for it. They did eventually turn around and give it away but IIRC it was under a year from release and they expected me to buy a whole other game.

Roboquest is one of my fave co-op experiences in recent years

Darktide is fire, it's a left 4 dead style game (horde shooter?). If you want 2d shooters, I really enjoyed Broforce and Huntdown (that one's a real gem)

check out:
Ink Inside On steam.
It's a couch co-op action RPG with ranged combat meets beat em up fights. Aesthetic is 2014 cartoon network, with a story based on a lost Nickelodeon pilot. Voice cast is solid with Brian David Gilbert too.
If it sounds interesting, could definitley be up your alley!

Synthetik. Insane coop shooter that has the most dopamine inducing gameplay I've ever experienced.
Out of all the games here, this one is the absolute hidden gem. Because nobody has heard about it. But they absolutely should.
- I only know about it because Ssethtzeentach made a video about it. Dude is the king of finding random games you've never heard of that are totally awesome. Kenshi, too.
- Which one are you referring to:
  Synthetik: Area (free to play): https://store.steampowered.com/app/984110/SYNTHETIK_Arena/
  Synthetik: Legion Rising: https://store.steampowered.com/app/528230/SYNTHETIK_Legion_Rising/
  Synthetik 2: https://store.steampowered.com/app/1471410/SYNTHETIK_2/
  I’m interested in the top down kind of style, I was expecting an FPS but this could be fun.
  
  I have played the 2nd one only. The 3rd one has the classic early access tag with the last update being released more than a year ago.

So, you're essentially looking for games like Borderlands, do you want more RPG in it or less?

Earth Defence Force. Basically, you are participating in a B-movie scenario, with UFOs, kaiju, giant ants, flamethrower clams, and winged frogs. It is quite a good time, and the higher difficulties require genuine skill and cooperation.
EDF 6 is the best in the series from a gameplay standpoint, but is far weaker than 4 or 5 when it comes to the level design + narrative. Still, the QOL pushes the game to the next level, especially if you got pals to tackle the missions. There many different weapons, not just in power, but also shot pattern, reload style, knockback, and so forth. Also, there WILL be hundreds of enemies on onscreen at any given moment. Each of the four classes have very distinct characteristics when it comes to loadout, mobility, and purpose, so you should be able to find a good match for yourself.
Earth Defense Force 6 - trailer
- Yeah. My kids and I play this together. It's a lot of fun. It's not as thinky as some other games but for a quick hour or two, it's a blast.
- I'm not really sure EDF 6 is the best entry point to the series, as it's a direct sequel to EDF 5. I think it will get really confusing story- and missionwise, more so than it already is. EDF 5 was a soft reboot and is also a bit cheaper.
  My friends and I really liked the WORLD BROTHERS 2 spinoff too, if someone is looking to play with a young player that might be a better starting point than the mainline games. The rest of the series spinoffs have not really done it for us.

Remnant: From the Ashes gets my vote. It's a superb co-op shooter despite getting somewhat repetitive near the end. There's also a sequel that seems to be well liked but I never got around to playing it.
- I found the solo play of both Remnant games really unsatisfying. Slow pacing, uninteresting enemies. Is it much better with friends?
  
  I haven't played much of singleplayer but I did find it engaging with friends, especially the bosses.
- If you enjoyed Remnant then it's definitely worth picking up Remnant 2. Remnant 2 improves on everything that was great about Remnant.
  
  Can you elaborate? Specifically because almost all of the negative Steam reviews, of which there are many, say more or less the opposite - that it tries to do that, but fails to capture what made Remnant so good.
  (Not to criticize your opinion, to be clear; it's on sale and I was strongly considering it as someone who likes Remnant. Sell it for me?)

Prodeus is a fun multiplayer DOOM-like with old school vibes
- Is there a possibility to play a campaign in online coop?
  
  Yup!

Halo. Not a hidden gem, but locked to xbox for a long time. (At least, co-op was.)
Best way to play is probably local co-op, but I imagine online is good too. Local co-op is only available on console sadly. Mysteriously.

Does Portal 2 count…?
I remember enjoying Left 4 Dead back in the day.

Rainbow Six Vegas and Splinter Cell Blacklist and Chaos Theory were awesome for this - especially for 2 people.
If you have 4 then SWAT 4, Ready Or Not, Operation Flashpoint: Dragon Rising, ARMA 3.

Halo series
Gears of war series
Army of two
Risk of rain 2

I always loved ARC - Attack, Retrieve, Capture - originally from Hoopy Entertainment and then PopCap. You joined an ad hoc team and piloted a little flying saucer around a maze, shooting at the other team's saucers. It was super simple to learn and wonderfully addictive. Probably not around anymore. I knew the two guys who created it.

Halo Reach, baby. That's the king.
- Plus all the Halos before, yeah. Unfortunately online co-op on the master chief collection just would not function properly for me and a friend which was devastating
  
  I've heard that was an issue years ago, and fixed. We were able to play thru every game fine.

I'm not into these, even though I try them from time to time. But one was actually a looooot of fun - Shadow Warrior 2. The gunplay, the chaos, it was extremely entertaining!
And it only costs a few bucks.
- Shadow Warrior 2 is so fun, I was and still am so disappointed they scrapped co-op for the third one.

Timesplitters 2 and 3 for some older stuff. They’re spiritual successors to Goldeneye (made by mostly the same people) and they both feature fun coop campaigns. Shouldn’t be too difficult to emulate.

CRAB CHAMPIONS
- True gem of a game

Ready or Not
Six Days in Fallujah
Halo
Halo is an all time great and especially for co-op.
- Seconding ready or not, had an absolute blast with it, both solo and coop !
- Six Days is…an interesting choice

Splatoon 3 Salmon Run

SWAT 4

Post linked on my list of many requests for gaming suggestions that got answers at !videogamesuggestions@lemmy.zip

Payday 2/3, Helldivers 2, Deep Rock Galactic, Ready or Not

If you can get past its extremely questionable social issues, I've never played a co-op combat game as well designed and implemented as resident evil 5. It forces you to work together in a variety of challenges and unexpected ways. It keeps you both focused on mutual goals. And if you don't work together with situational awareness and effective communication, you will not succeed. I really wish it sold better because I've never seen a company since put as much effort into co-op design except maybe the "it takes two" and "a way out" guy. But those aren't shooters.
- Your mileage may vary, but there's a bug on the PC version that causes a boss to regenerate health tied to the frame rate. It happened to a friend and me, and we watched it happen to two other friends. Higher frame rates cause it to regen faster. There's a way you can cheese the fight to get around this, but maybe the method would be a spoiler.
  (Also, I thought this game was bad and not in an interesting way like its successor is, but once again, your mileage may vary.)
  
  I can certainly understand not liking it. Besides it's offensive social takes, it's definitely not what a typical Resident Evil game is supposed to be. But a buddy and I spent years trying to find good coop game experiences and as far as games that actually sculpt and tend to the coop part as opposed to just throwing a coop mode in at the last moment, very few come anywhere close to the effort to put into this one. On harder difficulties it's actually a really interesting challenge that's not just about bullet sponges or grinding for better gear but about strategy and effective teamwork.

I seem to remember liking Resistance: Fall of Man, but it isn't something you'll play over and over. But the couch co-op story mode was fun to play with my partner back in 2007 or so.
A Way Out was fun recently for couch co-op story as well, but I'm not sure if that is the type of shooter you are looking for. I had never played a game like it before, was pretty cool.

I still like warframe, even though it has a few headaches in there that make it more annoying than it needs to be. I don't want to trade my ducat fodder or passive rep for slots and potatoes every time a new update comes out. But I do like dressing up my space dolls and blasting my trumna for hours on end

Play Halo 1 on easy, no shooting allowed, only melee, and speed run it.

Some of the best co-op I ever played was in Rainbow Six 3, but I played with 7 players, and I don't remember if it will let you mix and match humans with bots on your squad. You'll need a gaming VPN to play co-op, also, since the servers are gone.
Halo is always a good time, as is Gears of War, and it kind of sucks that outside of Borderlands, these are the most recent recommendations I can come up with, but this genre has been left to rot in live service hell.