What are some lesser known games you recommend to anybody?

Playing the Mafia games myself at the moment, but they are fairly popular.

Should try HomeFront, the 2nd one I found fantastic despite the bad reviews I had heard about it:
https://store.steampowered.com/app/223100/Homefront_The_Revolution/
Actually won it from a giveaway here and still probably my #1 favourite of my winnings.

Another one is Spec Ops
https://store.steampowered.com/app/50300/Spec_Ops_The_Line/
Great story in that, though that isn't much of a sleeper hit, more a well known hit.

Also thanks for the giveaway!

https://store.steampowered.com/app/243160/Mushroom_11/

https://store.steampowered.com/app/359040/The_Music_Machine/

https://www.gog.com/en/game/outwars

https://www.gog.com/en/game/legend_of_kyrandia

EDIT: If you have a PS2 or you're not opposed to emulators, you should play these two gems:

https://en.wikipedia.org/wiki/Cold_Winter
https://en.wikipedia.org/wiki/Urban_Chaos:_Riot_Response

Thanks for the giveaway. 😎

Just some game i really enjoy to paly who come in mind
Hope you can find something ^^

I don't understand the review for the 2 first title but to me they are great game :)
This is the Zodiac Speaking
I Am Alive
Omno
Of Bird and Cage
Apsulov: End of Gods

Dead
Vomitoreum

depends really what you are looking, found the tokyo extreme racer series for myself, playing reventure recently and finished leisure suit larry wet dreams dont dry

Sutte Hakkun is my favorite game, and maybe I'm just in the wrong circles, but few people seem to talk about it despite the English patch, so I think it qualifies.

If you want PC games, there's Bullet Maze (an Adobe Flash game) and Mitoosis, both of which are free. If you want non-browser games and you haven't been keeping up with the "paid now-free games" threads, there's Little Square Things, which is on Steam and also free.

https://store.steampowered.com/app/323380/The_Magic_Circle/

Meridian: New World (RTS)
Unloved (FPS)
Break Stuff With Coins (physics based game)

Must play before dead 😂
Sleeping Dogs: Definitive Edition
Mad Max
Sigma Theory: Global Cold War
SWAT 4
Dead In Bermuda
Human Resource Machine
Machinarium

Should try:
Oxenfree
Serial Cleaner
OUT OF THE BOX
Timelie
Stories Untold

Alpha Protocol
Binary Domain
in a way: The Witcher 1 (haven't played 2, but the zeitgeist is that only the 3rd exists)
Arcanum of Magic and Steamworks Obscura: Steampunk cRPG from the era of Baldur's Gate and Fallout 1-2, but often forgotten. Needs the unofficial patch, but it's a beauty.

I'm not reallly good at recommending newer games that aren't visible enough to be in a monthly or another bundle, sorry. Still trying to catch up with the popular, well-received ones, but according to my reviews I mostly play disappointing games :|

It mostly depends of the genres you like, but...
https://store.steampowered.com/app/274520/Darkwood/ (2d horror... really hard)
https://store.steampowered.com/app/1304680/Voidigo/ (One of my favorite roguelites)
https://store.steampowered.com/app/960980/Apsulov_End_of_Gods/ (Great horror game)
https://store.steampowered.com/app/757320/Atomicrops/ (The most chaotic game I have ever played)
https://store.steampowered.com/app/585710/Blazing_Beaks/ (A really original roguelite)
https://store.steampowered.com/app/555220/Detention/ (A horror game that is more about the experience than being scared)
https://store.steampowered.com/app/433550/DARQ_Complete_Edition/ (Puzzle/"horror" game that's really original and looks awesome)
https://store.steampowered.com/app/940910/Minoria/ (I had a lot of fun playing this metroidvania. Maybe it lacks of difficulty, but I didn't get bored for a second)
https://store.steampowered.com/app/998740/Ring_of_Pain/ (This one is more about if you like this kind of game, but it was an addiction for me)
https://store.steampowered.com/app/439190/Stories_The_Path_of_Destinies/ (A big surprise for me. You could get bored if you are a completionist, but if you want to focus in finishing the main plot, it is a great experience... Good story, good fighting mechanics)
https://store.steampowered.com/app/418300/Wick/ (A short horror experience. It is pretty straightforward, but it accomplish what it tries with excellence)
https://store.steampowered.com/app/692890/Roboquest/ (A really fast paced fps... Oh, also a co-op roguelite)

And then some more known games but I think they desserver more recognition
https://store.steampowered.com/app/1217060/Gunfire_Reborn/ (one of the best fps I have ever played)
https://store.steampowered.com/app/480490/Prey/ (You probably know this, but in case you don't, PLAY IT)
https://store.steampowered.com/app/774361/Blasphemous/ (My favourite metroidvania/soulslike game)
https://store.steampowered.com/app/48000/LIMBO/ (I would say it is my favorite 2d puzzle game)

heat signature definitely. cheap as hell and great game. will add more if I recall something else

have you try this :

1. https://store.steampowered.com/app/105600/Terraria/
2. https://store.steampowered.com/bundle/20773/The_Room_Collection/
3. https://store.steampowered.com/app/1016920/Unrailed/
4. https://store.steampowered.com/app/881100/Noita/
5. https://store.steampowered.com/bundle/16355/The_Desperados__Helldorado_Wild_West_Bundle/

Freedom Fighters looks really competent (except the textures) even in our times of rushed AAA games. Not bad but still 15 euros for some reason, despite being launched in 2003. Cool giveaway too, I approve.
Edit: Forgot to add a lesser known game but still cool: Flashback. It was available on GOG for free as a part of their Summer Sale. It's a platformer game, 2D from the 1990's, which got ported to PC.

Some of this were actually famous once, but might be forgotten now. So here is my list, with my 97.7%-objective scores:

1. World of Goo, 95/100. Very whimsical, and levels have nice variety.
2. Unavowed, 94/100. Very well written story, with great party companions.
3. Heaven's Vault, 93/100. A game to slowly savor, great music and writing, nice graphics.
4. Papo and Yo, 91/100. Surprised me.
5. The Cat Lady, 90/100. The interface is a bit cumbersome, but the story and characters are incredible (supported by stellar voice acting). Also, the graphics might look crude, but they do support the story.
6. Baba is You, 89/100. One of the smartest puzzle game ever made.
7. Cryostasis, 89/100. It's cool.
8. Crypt of the Necrodancer, 89/100. RPG-rhythm-roguelike game.
9. Ghost of a Tale, 89/100. Inventive world with rats.

Honorable mentions to some games people have mentioned in the thread: Driftmoon, Timelie, The Magic Circle are all 88/100 in my book, and are indeed awesome and a bit forgotten. And a shout out to Blades of Time, 86/100, which I just finished -- the critic reviews are pretty bad, but I enjoyed myself a great deal with it.

Some gems that most people dont know about are: Mad Max,Driver:San Francisco(Ubisoft is about to kill it soon),Spec Ops:The Line,Sleeping Dogs,and Vampyr.

Out of the blue will recommend these two titles (story wise they can be called poor, but in terms of gameplay they are excellent representatives of their genres):

Rogue Fable III - it is a rogue-like game that doesn't require a lot of time for one run with great variability and replay value. You can try original game on Armorgames in your browser, though it slightly different from the Steam version.

ARMORED HEAD - I believe every arena shooters lover should give it a try, it can be both: an excellent one time experience or a pleasant aim trainer for your future wins in various FPS. There is a good value for its price, especially if you will get the game during sale.

Coin crypt as a roguelike, maybe?

There was this yakuza car game I used to play on Xbox so don´t know if they even made it for pc or not that was really nice but due to the release date it might be hard to find.
Wolfenstein,Life is Strange and a Plague Tale are some games that I ended up liking when at start I was like am I really playing this? Even though they are known they sometimes go under the radar so

Vampire Survivors, I really like how chaotic it is.

Yoku's Island Express is amazing.

Zeno Clash, very weird with a dreamlike atmosphere and good gameplay.
https://store.steampowered.com/app/22200/Zeno_Clash/
(Same dev that Rock of Ages if you know about it).

Unexplored 2
The Gunk