Secret because they are hardly known by anyone. This list has my own system of standards for how to pick some games out of a thousand possibilities.
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This game looks like it could potentially be enjoyed by children @Pifanjr
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@Colif is this the one we discussed the other day?
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@Kaamos_Llama may want to check this retro shooter
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Game's With Demos

Warfare Legacy Collection on Steam
Warfare 1917 and 1944 return, fully remastered with enhanced visuals, full-screen support, and custom battles. Warfare Legacy Collection also Includes the Battle of the Bulge, a brand-new campaign set during WWII’s final offensive with all-new missions, snowy maps, and intense front-line action.

Save 25% on Survivalist: Invisible Strain on Steam
It's ten years since the infection started. Long-established settlements are collapsing, one by one, for unknown reasons. Survivors are running to the hills to escape, hoping for safety in remote places. As another refugee, you're here to carve out a new life for yourself - by any means necessary.

True Fear: Forsaken Souls Part 3 on Steam
True Fear: Forsaken Souls Part 3 is the final chapter of the psychological thriller trilogy. With point-and-click mechanics, intricate puzzles, and cinematic cutscenes, immerse yourself in a dark horror experience that redefines the genre.

REPOSE on Steam
In the facility, each step, each shot, each mistake costs precious energy. Rendered entirely in black and white, this mystery can be unravelled. The puzzle can be solved. Don't ask who tried to solve it before. Do the job. Find oxygen and sleep. Go deeper. And don't ask about Aaron.

Remote Reaper: FPV Drone on Steam
FPV drone simulator. Destroy enemy vehicles with high-precision strikes. Simulation of electronic warfare and realistic armor model.

BLACKSHARD on Steam
BLACKSHARD is a first-person exploration game. Wander through a strange megastructure, the Labyrinth, to unravel its mysteries... Your behavior within the Labyrinth will define the outcome of your journey. What path will you choose to take?

Lost For Swords on Steam
Lost For Swords is a Roguelike Deckbuilder, where the cards in your deck shape the rooms you’re exploring. Make your way up the tower, equip weapons and armor, cast spells and scrolls, activate auras, collect loot and defeat monsters in tactical turn-based combat.

Office Simulator on Steam
Ready to climb the career ladder? In Office Simulator, start as an intern and rise through the corporate ranks. Gain experience, earn promotions, and when the time comes, launch your own company to begin a new business adventure.
Games Without Demos

Human Fast Food on Steam
A cooking simulator where you run an underground fast food for monsters and serve them with human meat. Improve your kitchen appliances, unlock new recipes, manage your stock and keep the monsters well fed.

Pub Toilet Simulator 25 on Steam
In Pub Toilet Simulator 25, you're trapped in Spetherwoons pub, racing to find a toilet. Navigate endless hallways, tricky stairs, and bizarre tunnels while keeping your beer meter full. Grab pub food for points, but don’t waste time! Every wrong turn brings you closer to disaster. Will you make it?

Get a midnight snack without mom knowing on Steam
Find delicious food in the dark kitchen. But you have to move as carefully as possible. My mom may wake up.

Save 10% on Versebound on Steam
Slay hordes of enemies and fight mythical bosses in this challenging action roguelike. In a desperate fight for survival you must perform rituals, buildcraft and learn from every misstep to become stronger. Use unique abilities and powerful artifacts to beat every trial in the world of Kalevala!

XENOBREAKERS: Classic Tower Defense on Steam
Defend Billy and his crew on their way to the extraction zone! You have been authorized to use the defense system. Protect them from giant bugs, malfunctioning droids and more...

Save 20% on Brány Skeldalu on Steam
Gates of Skeldal is a cult classic Czech dungeon crawler from 1998. On the mythical island of Rovenland, a party of adventurers sets out to stop five rogue mages from the tower of Skeldal. Enjoy turn-based combat, powerful magic, and tricky puzzles in this legendary RPG!

Many Nights a Whisper on Steam
A short interactive essay on dreams, pressure, and expectations. Take part in an ancient ritual where one shot determines the fate of a generation.

LiDAR Exploration Program on Steam
LiDAR Exploration Program is a relaxing atmospheric game with light horror elements, where you explore in complete darkness using a scanner to reveal the world around you.

Maestro's Cold War 2 on Steam
Revive the Cold War in this classic strategy game—easy to pick up, yet challenging and deep, offering endless replayability.

Carnival Heroes - Super party minigames on Steam
Cross-platform online multiplayer board game for 2 to 4 players similar to super mario party. Collect crowns, gems, items and be the best in minigames. Play in 23 minigames in online and solo mode. Race with others, fight, shoot, catch, test your memory, and have fun.

Fortune Avenue on Steam
A competitive board game where players vote to shape their destiny. Transform caravans into 5-star hotels, collect wonders, and earn bounties for bankrupting opponents. Use airports to outmaneuver rivals, organize World Cups to multiply your rent. Can you turn your empire into a global monopoly?

Delos: Space Traffic Control on Steam
In Delos, you are the space traffic controller managing the flow of ships at a bustling space station. Direct docking, allocate resources, and prevent collisions in a real-time strategy setting. Balance efficiency and safety to maintain order in the interstellar hub.

Detective Penguin on Steam
Detective Penguin is the first and only physics-and-penguin-based detective game on the market. Solve cases in your own way. Interrogate suspects, find clues, or use your flippers to punch your way to the answers.

Assemblands on Steam
Build your factory from zero and produce high-tech products like drones, PC, robots and compete against thousands of players.
@mjs warlord here's another factory game

EarWorm on Steam
You are an Earworm. You are an underworld contractor who hacks memories for a living. Dive into the memories of your victims in order to unlock the security questions to their bank account.

Tranquil Isle on Steam
Tranquil Isle is a lo-fi strategic townbuilder. Create cozy little settlements on the sun-kissed shores of your very own island paradise.

Shoot The Wall on Steam
Shoot the wall! Simple, right? Use your gun to blast your way through the wall, upgrade and change your weapons so you can shoot your way through the wall even faster! I mean come on, you've gotta know what's behind that wall, right? 4 Parts 4 Walls 4 Endings Free DLC on the way!

The Boba Teashop on Steam
A cozy horror game where you own and manage a boba tea shop. Prepare boba teas, serve customers, and expand your menu to grow your business.

Duriano on Steam
Duriano is a top-down arena shooting Slasher roguelite game where the player will be a hero durian of the norse wielding a weapon to fight upon a god of norse mythology. From different weapons, Durian hero, God’s trail, items will lead the player to create a build and defeat all gods of asgard.

Neongarten on Steam
A minimalist cyberpunk city builder inspired by Islanders and Luck Be a Landlord.

Save 10% on Mother Hub on Steam
A retro FPS with an artistically gritty setting from the early 2000's. Uncover futuristic weapons lost to time and face off against terrifying bosses. Do you have what it takes to stand against the darkness and save humanity from the brink of extinction?

Replicube on Steam
Replicube is an open-ended programming puzzle game/toy about writing code to replicate 3D voxel-based objects. Solve puzzles, pursue leaderboard glory, or just make art to share with the in-game community.

SignaNota on Steam
Experience charming pixel art and a new style of combat — unfold a rogue-like adventure with 'Slingshot Action' in SignaNota.