I just got and am obsessed with UnderMine, an adorable roguelite dungeon crawler a la Binding of Isaac. Currently on sale for $5!

A few to add in:

Solasta: Crown of the Magister - Old school D&D and tactics RPG. It’s indie so has rough edges here and there, but it’s so fun, and there aren’t a ton of games that fill the void.

Dungeon of the Endless - It’s a tower defense / tactical game with great pixel art and one of the best soundtracks I’ve ever heard.

Battle Chasers: Nightwar - Excellent RPG that will remind you of old school Final Fantasy.

Tower of Time - Excellent tactical RPG

Detroit: Become Human - Cinematic narrative game about androids becoming self aware.

The Dark Anthology: Man of Medan - Cinematic narrative horror game, the first in a series of several, therefore if you enjoy there’s a lot more where that came from. (Made by the same studio that created Until Dawn.)

Norco! It’s this post-apocalyptic Southern gothic point and click game. I downloaded the demo and got hooked.

I suppose it depends on what a person considers a hidden gem because everyone's tastes are different. I'll list a few categories and at least 1-2 of my favorites in those categories that I've found on Steam and are currently on sale:

Exploration/Base-Building:

• Grounded
• Raft
• Rimworld
• Subnautica/Subnautica: Below Zero

Story based/Farming/Romance:

• My Time at Portia*
• My Time at Sandrock

Visual Novels:

• Basically anything made by PixelFade (Ace Academy, Ethereal Enigma, Crystalline). One of the few English-based VNs that are fully voiced in English and have a pretty decent plot/story. Interactive with different choices affecting different outcomes and even some minigames at least in EE.
• Nekop er Hush Hush. Ok, listen. I won't beat around the bush here. There IS an 18+ DLC for this but it's not necessary to enjoy the game. It honestly has a pretty interesting story/premise and I did get pretty heavily emotionally invested in the characters.

*Note that MTAP has been fraught with issues. Although these issues don't necessarily make the game unplayable, and it's still enjoyable, be aware that it is was Pathea's (the studio) first such attempt and as such they were still learning. Their second game Sandrock has solved a lot of the issues and it's not necessary to play the first one

If you're a fan of co-op survival and adventure games, Grounded is great. There's also Raft which is a more chill style adventure game.

Personally I'm probably picking up in this sale:

• System Shock
• Outer Wilds
• Aquatico
• Pummel Party
• The Long Dark: Survival Edition
• A Way Out
• Phasmophobia
• Halo: The Master Chief Collection
• Voidtrain

just grabbed god of war, disco elysium, and hellblade senuas sacrifice...

as far as recommendations go, Mass Effect legendary edition and dragon age are very enjoyable if you like RPG with a focus on lore, story and characters. Red Dead Redemption 2 is a wonder and a steal at $20. Witcher 3 for $12. Horizon Zero Dawn for $16.50

I've already got a Steam Deck and I really enjoy it, but I've been eyeing the Dock for a while too. It's on sale now for even less than the alternative I was considering so I'm probably going to grab one very soon

Wytchwood is a fun crafting adventure game with a lot of fetching. Not too long of a game either and I finished it in a few days.

Here are a few that I really enjoy (though their level of "unknown-ness" is debatable):

Mini Metro: https://store.steampowered.com/app/1127500/?snr=1_5_9__205

Demeo: https://store.steampowered.com/app/1484280/?snr=1_5_9__205

Evoland: https://store.steampowered.com/app/1020470/?snr=1_5_9__205

I'm going to come in with some actual more hidden gems:

• Megabyte Punch

• Dorfromantik

• Hatchwell

• Imposter Factory (and the whole series)

Super Blood Hockey. 80% off, about $3 USD.

It's a very well made pixel art game where you play hockey and you can beat up the other team. There's a franchise mode as well, so you'll want to balance how much fighting you do so your players don't get too hurt. There's local co-op so you can play against friends (or use steam remote play together).

PlateUp!. 40% off, about $11 USD.

Similar to Overcooked but you need to manage your restaurant and make sure you don't fail a single order. It's a rouge-lite, and you can move everything around in your restaurant and you kind of manage the menu as the days go on, but you get a choice whether to add option A or B, so it slowly gets more complicated. Very fun with friends, steam remote play together works here as well.

Bone's Cafe. 30% off, about $11 USD.

Similar to Overcooked and PlateUp!, but I feel like it's more geared towards single player (but there's local co-op as well). You have to manage your restaurant and menu (can make it as easy or complex as you'd like), while also maybe killing customers to harvest them for ingredients :) You can spawn in helpers and you can show them a repetitive task to do and they will do it.

I'm really enjoying The Tenants, no idea if it's a hidden gem or not. It's like House Flipper but also a bit Simsish. You renovate properties, negotiate leases and manage tenants. Good fun!