• Majora's Mask: a 3-day timeloop where everything resets when you go back

• Katamari: A giant ball gets rolled around and collects stuff forever

• Baba Is You: Movable text is rules to the game

• Untitled Goose Game: You have to piss people off the right way

• Billie Bust Up^[unreleased]^: Musicals tell you upcoming platforming challenges

• Celeste: every time you die you quickly reset on the same "page"/small tile of map

• Splatoon: you shoot at the ground to go faster, hide, and/or win

• Odama: real-time tactical wargame pinball

• Golf Story: Golf-based fetch quests

• Astral Chain: asynchronously control a companion in combat

• Okami: paint skills on-screen in combat

• Astro Bears: Snake but in 3D

• Lovers In A Dangerous Spacetime: Up to 4 players pilot parts of a ship together

• Pokemon Ranger: draw circles around monsters to catch them

• Viva Pinata: breed pinatas to create new species

• Spore: create and evolve a creature

Tunic is incredibly unique and I can't say I've played anything like it. On the surface it's a classic dungeon crawler zelda inspired thing, but once you play.... Really any amount of it, you start to see past the veil and the real game is revealed to you. Even after completing the entire game and all achievements, there is technically more of the game available to be explored.

Outer Wilds (not to be confused with Obsidian's Outer Worlds) will be an absolute bliss for anyone who enjoyed portal or superliminal. It may be the single greatest puzzle/exploration game ever made, with no exaggeration.

Return of the Obra Dinn was a game that I could not put down. I played it in one sitting beginning to end. I was enthralled and I felt like Sherlock fucking Holmes. It is a very unassuming game but by God, you will be gripped. It stands up there with Outer Wilds as being a game that absolutely propelled itsself up to one of the best of its genre (this one being Mystery/Puzzle)

Fez: a 2D plateformer in which you can change the perspective to create ways to unreachable plateforms

Baba Is You: a puzzle game in which you move blocks with words written on them, combining them to create small phrases which become new rules of the game.

Impossible Creatures - an RTS where you slurp up DNA from local wildlife and use that to create weird hybrids of multiple animals, then produce those as units that you control to complete missions. Great concept but I think it ended up being a bit unbalanced.

Papers Please - pretty unique gameplay in that you had to literally read through paperwork and approve/reject people at a border crossing. Good social commentary.

Katamari Damacy - The objective is to roll a ball-like thing called a katamari, to roll up objects, and make the katamari bigger and bigger. You can roll up anything from paper clips and snacks in the house, to telephone poles and buildings in the town, to even living creatures such as people and animals. Once the katamari is complete, it will turn into a star that colors the night sky. Sounds weird, but it's super fun, trust me. Plus, it's soundtrack is kickass.

Factorio - its a logistics rts but the pollution mechanic is different. Instead of just gather resources to build things which build bigger things, you also make pollution as a side effect. This feeds the native monsters and also evolves them. Managing your pollution cloud is a strategy. That or build massive defensives for when they come to eat you.

Tunic and Outer Wilds

Both have a heavy focus on using knowledge as your core resource in the game, and obtaining new knowledge as a primary gameplay loop.

Faster than light - manage crew in a 2D strategy environment and jump around in space. Pretty unique gameplay which only recently got some clones.

Teardown - Work as criminal stealing stuff, but the clue is you can destroy everything and you need to create smart parkour to steal stuff right in time before the cops arrive. Also you can sandbox play it if you get bored.

Terra Nil - Bring back nature to a destroyed earth, with relaxing and calm mechanics. Highly recommend.

Others: FEZ, solve puzzles. Deep Rock Galactic, because dwarfs being this much dwarf is just dwarftastic. Rock and Stone!

In Return of the Obra Dinn you play an insurance claims investigator. You can magically view the moment of somebody's death and hear the audio prior to it to aid in your investigation of a ghost ship.

Maybe Antichamber? It‘s a first-person puzzle game like Portal, but based on the idea of the „rooms“ changing as you go through them, so each room basically has its own mechanic to figure out

Return of the Obra Dinn.

Wow. I'm super impressed with all the suggestions here. I'll add a few of my own that haven't been mentioned yet.

Her Story - you query a police archive database for video clips, eventually revealing the plot. Kind of a mash between a murder mystery book with the pages out of order and Google. If you like it, check out Immortality

What Remains of Edith Finch - all you can do is walk around a very unusual house. The narrative reveals itself as you do so. That narrative is fantastical and heartbreaking and also very sweet.

Crawl - multiplayer game - you are all trying to escape a monster and trap filled dungeon. One of you is alive and the rest are spirits who can possess the monsters and traps. Any time a spirit kills the living player, they become the living player. Unique boss fight at the end where multiple spirits control parts of a huge boss monster.

Death Stranding

I've never played such a unique big budget game. The core mechanic is terrain traversal to make deliveries, and the game continues to give you tools throughout it to accomplish that.

I remember ‘Braid’ being very good. A number of different time manipulation mechanics throughout the different levels of the game. Puzzle platformer.

There’s an anniversary edition planned so maybe stick it on a wish list for now.

Cultist Simulator is pretty unique... not necessarily in a good way. It's a storytelling/puzzle game with some great writing if you can power your way through the gameplay. The mechanics are deliberately very obtuse, with no tutorial, to emulate the fact that diving into the occult is confusing and dangerous. The end result is that the game is very unique and cool, but it's absolutely not for everyone. TL;DR on the basic mechanics: you have a handful of verb boxes, such as Talk or Research, as well as various cards that you can slot into them. Each card has a variety of tags on it. Depending on which cards with which tags you put into the various verb boxes, you get different results.

Outer Wilds is amazing and the mechanic is unique.

Heaven's Vault

You play a space archaeologist, and the big central mechanic of the game is translating things written in the Ancient language.

Ancient is written using ideographs, and more complex ideas are represented by combining glyphs that describe the concept, like ever more complex compound words. There are art of speech markers, glyphs that describe how other glyphs in a word relate to each other, intensifiers, and even a few cases where super common words are just the combination of other basic glyphs into a single composite like a Norse bindrune (for example the symbols for creature and knowledge overlap to make person, an intelligent creature). 46 base ideographs, but that includes digits, so it's only 10 more than English.

So for example, a word that reads NOUN-person-Sub/Obj CONNECTOR-NOUN-knowledge-person means "Emperor", because noun-knowledge-person means "law" and thus the result is a person who the law belongs to, aka a ruler or in the context of an empire the emperor. Replace that noun marker glyph at the beginning with the adjective marker glyph and you would have "imperial", the quality of being emperor-like.

One of the longest words to appear in the game translates as "mouse" and it's 21 letters long and is literally something like creature-CONNECTOR-many-many-Sub/Obj CONNECTOR-ADJECTIVE-NOT-ADJECTIVE-CONNECTOR-many-creature-CONNECTOR-ADJECTIVE-ABSTRACT NOUN-person-CONNECTOR-light-NOUN-plant-CONNECTOR-rock, which is several words stitched into a compound word, where some of those words are themselves compound words (the idea is something like "creature like a very small pig", but the word I'm calling "pig" means "creature that is happy in the soil" where happy is something like "the quality of a person who is metaphorically full of light" and "soil" is "plant-earth"). Those CONNECTORS are letters that are used to build compound words.

Qube and anti-chamber if you're a fan of superluminal

Exapunks is a programming puzzle game set in a retrofuturistic cyberpunk world with early '90s aesthetic. The tutorial is in a form of an in-world zine. For me it was very immersive.

Prison Architect is pretty cool and unique.

Portal reloaded adds time portals ontop of the normal portals.

Splitgate is an FPS that adds portals on top of Halo style combat. Very fun but may be hard to find a game these days its kinda dead.

Age of empires 3 is an RTS that adds shipments. These shipments increase the pace of the early game and allow for way more personalized play as well as allowing players to react to different things without shifting their entire build order.

GTFO is a horror fps where you and 3 other human players take on raids and these raids are changed each season. When the raids are retired they are gone. You must beat the lvl 1 raids to unlock lvl 2 and so on.

Radio Commander. Its an RTS where you sit in a tent in Vietnam and give and recieve orders via radio. You have a map that you can mark where things are based on the info you get.

Getting Over It - the controls themselves are your enemy. A different take on the same concept: Octodad / Manual Samuel.

Kenshi has a lot of unique elements. It's sort of like a post-apocalyptic Sims game.

It's very addictive and is one of those kinds of games that surpises you with how much freedom you're given. I've not really seen anything quite like it.

Neon White: A parkour FPS puzzle game where you cards are your weapons

Rollerdrome: Best way I've heard is described is: Doom x Tony Hawk

I really love Terra Nil.

You basically have to restore a wasteland back to lush, green nature.

Much like a city builder, this is achieved by putting down buildings. The twist is that at the end, you can't leave a trace so you need to demolish everything again.

It's not a long game, but I thought it was very satisfying. A relaxing puzzle/city builder with soothing music.

Before Your Eyes

The recently deceased Benjamin Brynn is on his way to the afterlife. The player must interact with Brynn's memories through an eye-tracking webcam to progress, as the game reads and responds to the player's eye movement and blinking - from Wikipedia

It tries to emulate life flashing by your eyes as you are dying. I haven't gotten around to play it but, the concept is cool nonetheless.

Found about it from this video - https://www.youtube.com/watch?v=LTI1WCopTsg

I have a couple kinda unique things to suggest. There is a small indie game called Eversion that you can find on Steam. The core mechanic is about shifting to these different planes of existence to finish levels. You can only shift at certain places and shifting opens up pathways that weren't there before. Its retro style graphics and otherwise very simple controls. The Turing Test is a puzzle game like Portal, but instead of portals, you have a gun that can be used to move energy orbs from around the rooms to unlock doors. The game feels like it encourages creative problem solving a lot more than most puzzle games. Catherine. Catherine is a game in a few styles. You spend part of the time at a diner/bar interacting with people. Then you go to sleep and in the dream world you ascend towers using moveable blocks that you must climb. Sometimes you are chased up the tower by a boss enemy. There is no combat in the game. It's about ascending the tower as fast as possible at night and progressing the story by day.

Graphwar is definitely unique. It's a bit like worms, but you fire mathematical functions.

Crypt of the Necrodancer: Roguelike to the beat! Dance pad compatible.

Do Not Feed The Monkeys - spy on people via hidden cameras for fun and profit. It's mostly point and click but it's fun.

Snake Pass - "What does a platformer look like without jump (or a regular walk for that matter)?" It's really fun and unique.

Poppy Playtime (2021) : controls the extendable arms separately and solve puzzles that way

Older games:

Psychonauts (2005) : some of the scenes toy around with gravity

Half-life 2 (2004): the gravity-gun was groundbreaking.

Serious Sam (2001) : just a shooter, but the quantity of enemies is so huge that you need to figure out different strategies. It's sort of like geometry wars only in first person view and with gory graphics.

Glover (1998) : it's a 3d platformer, where you control a glove, which needs to get ball through the level.

Head over heels (1987) : control the 2 characters Head or Heels separately or together to solve puzzles.( It was recently released on steam. I haven't tried the remake, but the original can also be found on emulators or online)

Against the Storm Rogue lite city survival builder with gorgeous art, awesome game mechanics and a fantastic dev team whom have basically built the game in collaboration with the community that’s risen around the game.

• Patrick's Parabox: Push blocks around to activate switches and reach the exit but the blocks can be pushed into and out of each other recursively, it's awesome
• Fez: Already been suggested so +1 for this, lovely game

The game is definitely not for everyone, but ProsperousUniverse kind of stands alone when it comes to people’s descriptions of niches/genres.

The game is an economy/real-time MMO with no real PvP. “Real-time” not like an RTS but as in “this operation takes many hours or days” and everyone has that same time burden.

It’s a game where planning far outperforms “always online” gameplay, so people end up learning spreadsheet software to optimize everything for themselves.

In addition, the UI is modular like a Bloomberg terminal, so it feels right—you feel like a trader.