That's a tough one! It's hard to choose among all the jewels that are in the indie plane. Each one for their own reason.

I will say: PIKUNIKU. Why?
Because for me it has been insanely fun.
I had fun playing solo. Its a simple game. Simple graphics, adorable. Simple story, but with deeper meaning and a social and enviromental positive message. Simple mechanics, though full of secrets on its levels and with amusing gameplay.With cheerful music simple and sometimes stupid characters, totally merry, on a good way. It can be played and enjoyed by all ages. It's a game full of charm.
I also had more fun playing its coop mode. Short levels to play with friends. There are levels you can compete, and levels you need to team up.
On the quarentine I streamed up and played with my nephew of 9 and also with my two best friends (grown-up people)
The game has troll moments too, the ones that make you smile, though.
So I found Pikuniku quite complete. It liven up depressing moments and I think it's quite complete with all this so, yeah. I will say Pikuniku.

My choice would be Yuppie Psycho, because it brings back the nostalgia of good point and click game
besides of also having a good and captivating story with multiple endings.

My favourite indie game is Mount & Blade Warband. Why? It's an incredible Historical Strategy Sandbox RPG, with a live and breathing world, where every playthrough will be different. You could be the leader of some bandits and terrorize small towns to stole they reaources, or lead a band of mercenaries that help the poors, you can conquest lands for a King or for your own Kingdom, raid Castles or defend you own, the possibilities are limitless.
Deep dive in the deep and realistic combat, were you have to learn how to shoot arrows or crossbows, use the directional sword combat and how to lead your units into battle, there are plenty of weapons at your disposal and different units that are more or less effective against other types, there is a lot to learn in this game.
You interesting just in combat? You can try the skirmish mode where you can create your own combat against different factions and try many combinations.
And if this is don't anough for you, you can install one of the thousands of mods available for this game: Lord of the Rings? Checked. Game of thrones? Checked. Japanese mod? Checked. WWII mods? Checked. Fantasy mods? Very checked. Graphics mods? Ultrachecked. Total conversions with story mode? Of course is checked. No enough violence? We have some gore mods for you. Unofficial expansions? Brytenwalda is there to give you more content. And the list can go on and on.
You want even more? There is a multiplayer mode if you are interested in that, nothing is more fun that play with friends!
For those and many things more Warband is my favourite indie game.

My favorite is Rimworld: for when you want Dwarf Fortress, but you'd rather fight the world than the interface.

And why? I'll repost my Steam review:

RUINER

The length of this game, the music, the art style and the subject matter where handled perfectly. It controls like a dream and though it is short the memory of it lingers properly.

My favorite indie game is To the Moon. A very unusual story - I love it very much.

I'd honestly say either Terraria or Children of Morta. The latter is literally an ARPG that's made for me (a story-driven individual) and the former is straight-up brilliance. I love how it's not just about building, it's about exploration. I'll never forget the first time myself and a friend delved into one of the procedurally-generated dungeons and found that it went so ridiculously far into the earth. I speculated and imagined what may have happened there and what its purpose might have been.

Paper Sorcerer was a game that impressed me. From simple but stylish aesthetics in black and "white", to a very nice story with a very interesting ending being the cherry on top.

Doujin counts as indie, right?
In which case, my favorite indie game of all time has gotta be Shoot the Bullet, for the simple reason that it provides such a wonderfully intense adrenaline rush.
I just love the feeling of pushing my brain to its limits, trying to extrapolate the trajectories of countless enemy bullets at once, to plot a safe course through the rapidly shifting bullet maze.

Furthermore, unlike most shmups, where failure can set you back as much as an hour's worth of play, failure in Shoot the Bullet seldom sets you back more than a couple minutes worth of progress, thanks to the game's bite-size scene-by-scene à la carte format. This allows the game to crank up the intensity a bit without making things too horribly frustrating (...usually), allowing for an exceptionally high ratio of adrenaline to cortisol.

Scenes 4-3, 4-8, 5-8, 6-5, 7-4, 8-3, 9-6, and 10-5 are all especially fun to score attack.

The top-notch action is combined with lovely visual and audio aesthetics, and a pleasantly lighthearted tone (you're shooting a camera, not a gun; meanwhile your opponents' colorful magic bullets are nonlethal, and being put on display at the player character's request).

I've just never found a single-player video game that provides quite as much fun as this one (aside from possibly its own sequel, Double Spoiler, but I've put very little time into that game, due to Wine issues).


But I doubt GOG'll choose an entry only citing a game that's not in their catalog, so I'll add that Crimzon Clover is also pretty darn great. :)

(Caladrius Blaze, Nex Machina, and REVOLVER360 look quite promising as well, but I haven't gotten around to actually playing those quite just yet...)

If they were to send me packing to Mars and I was told I could only bring one indie game with me to play for the rest of my life, it would definitely be Terraria. :) Why? Because for game with such a small digital footprint, it provides so much possibilities!

When feeling creative, Terraria becomes my canvas and I am free to experiment with building bases of all sorts: underwater, inside a cave, on tree tops, even up on a cloud.

When feeling curious, Terraria generates a gigantic world map for me to explore, with many biomes and hundreds of hidden treasure.

When feeling pumped, Terraria throws me into battle with goblin armies and hordes of zombies and kickass bosses.

When feeling lonesome, Terraria entertains me with quirky NPC's and adorable white bunnies.

When feeling bored, Terraria allows me to regenerate random new maps, discover community mods & maps, and invite friends to play/build/battle with me!

What Remains of Edith Finch because it challenges our view on storytelling by telling us a story of and about stories, a videogame anthology of sorts, in which each one is related to the others and enhances the meaning of the whole. It's really an enlightening and impressively creative and emotional title. Anything that Annapurna Interactive puts out is worth looking at but What Remains of Edith Finch is truly relevant to our understanding of narrative and the huge potential of interactive fiction. Love it to bits, bytes, and everything else afterwards.

RiME
RiME is an experience that takes us to a stylized and beautiful universe. Its apparent simplicity hides a depth that is revealed throughout the adventure. When traveling through the mysterious world of RiME, the action always takes place in a fluid and dynamic way. Controls are responsive, simple and intuitive. The puzzles are ingenious and always well framed. The soundtrack that accompanies the events and moments of the game is phenomenal. Visually the artistic direction is simply superb.
Those are the main reasons it's my favorite indie game. :)

Genesis is my favourite indie game because.

The Beginning

1 In the beginning God created the heavens and the earth. 2 Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters.

3 And God said, “Let there be light,” and there was light. 4 God saw that the light was good, and he separated the light from the darkness. 5 God called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day.

6 And God said, “Let there be a vault between the waters to separate water from water.” 7 So God made the vault and separated the water under the vault from the water above it. And it was so. 8 God called the vault “sky.” And there was evening, and there was morning—the second day.

9 And God said, “Let the water under the sky be gathered to one place, and let dry ground appear.” And it was so. 10 God called the dry ground “land,” and the gathered waters he called “seas.” And God saw that it was good.

11 Then God said, “Let the land produce vegetation: seed-bearing plants and trees on the land that bear fruit with seed in it, according to their various kinds.” And it was so. 12 The land produced vegetation: plants bearing seed according to their kinds and trees bearing fruit with seed in it according to their kinds. And God saw that it was good. 13 And there was evening, and there was morning—the third day.

14 And God said, “Let there be lights in the vault of the sky to separate the day from the night, and let them serve as signs to mark sacred times, and days and years, 15 and let them be lights in the vault of the sky to give light on the earth.” And it was so. 16 God made two great lights—the greater light to govern the day and the lesser light to govern the night. He also made the stars. 17 God set them in the vault of the sky to give light on the earth, 18 to govern the day and the night, and to separate light from darkness. And God saw that it was good. 19 And there was evening, and there was morning—the fourth day.

20 And God said, “Let the water teem with living creatures, and let birds fly above the earth across the vault of the sky.” 21 So God created the great creatures of the sea and every living thing with which the water teems and that moves about in it, according to their kinds, and every winged bird according to its kind. And God saw that it was good. 22 God blessed them and said, “Be fruitful and increase in number and fill the water in the seas, and let the birds increase on the earth.” 23 And there was evening, and there was morning—the fifth day.

24 And God said, “Let the land produce living creatures according to their kinds: the livestock, the creatures that move along the ground, and the wild animals, each according to its kind.” And it was so. 25 God made the wild animals according to their kinds, the livestock according to their kinds, and all the creatures that move along the ground according to their kinds. And God saw that it was good.

26 Then God said, “Let us make mankind in our image, in our likeness, so that they may rule over the fish in the sea and the birds in the sky, over the livestock and all the wild animals,[a] and over all the creatures that move along the ground.”

27
So God created mankind in his own image,
in the image of God he created them;
male and female he created them.

28 God blessed them and said to them, “Be fruitful and increase in number; fill the earth and subdue it. Rule over the fish in the sea and the birds in the sky and over every living creature that moves on the ground.”

29 Then God said, “I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food. 30 And to all the beasts of the earth and all the birds in the sky and all the creatures that move along the ground—everything that has the breath of life in it—I give every green plant for food.” And it was so.

31 God saw all that he had made, and it was very good. And there was evening, and there was morning—the sixth day.

2 Thus the heavens and the earth were completed in all their vast array.

2 By the seventh day God had finished the work he had been doing; so on the seventh day he rested from all his work. 3 Then God blessed the seventh day and made it holy, because on it he rested from all the work of creating that he had done.
Adam and Eve

4 This is the account of the heavens and the earth when they were created, when the Lord God made the earth and the heavens.

5 Now no shrub had yet appeared on the earth[a] and no plant had yet sprung up, for the Lord God had not sent rain on the earth and there was no one to work the ground, 6 but streams came up from the earth and watered the whole surface of the ground. 7 Then the Lord God formed a man[c] from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being.

8 Now the Lord God had planted a garden in the east, in Eden; and there he put the man he had formed. 9 The Lord God made all kinds of trees grow out of the ground—trees that were pleasing to the eye and good for food. In the middle of the garden were the tree of life and the tree of the knowledge of good and evil.

10 A river watering the garden flowed from Eden; from there it was separated into four headwaters. 11 The name of the first is the Pishon; it winds through the entire land of Havilah, where there is gold. 12 (The gold of that land is good; aromatic resin[d] and onyx are also there.) 13 The name of the second river is the Gihon; it winds through the entire land of Cush.[e] 14 The name of the third river is the Tigris; it runs along the east side of Ashur. And the fourth river is the Euphrates.

15 The Lord God took the man and put him in the Garden of Eden to work it and take care of it. 16 And the Lord God commanded the man, “You are free to eat from any tree in the garden; 17 but you must not eat from the tree of the knowledge of good and evil, for when you eat from it you will certainly die.”

18 The Lord God said, “It is not good for the man to be alone. I will make a helper suitable for him.”

19 Now the Lord God had formed out of the ground all the wild animals and all the birds in the sky. He brought them to the man to see what he would name them; and whatever the man called each living creature, that was its name. 20 So the man gave names to all the livestock, the birds in the sky and all the wild animals.

But for Adam[f] no suitable helper was found. 21 So the Lord God caused the man to fall into a deep sleep; and while he was sleeping, he took one of the man’s ribs[g] and then closed up the place with flesh. 22 Then the Lord God made a woman from the rib[h] he had taken out of the man, and he brought her to the man.

23 The man said,

“This is now bone of my bones
and flesh of my flesh;
she shall be called ‘woman,’
for she was taken out of man.”

24 That is why a man leaves his father and mother and is united to his wife, and they become one flesh.

25 Adam and his wife were both naked, and they felt no shame.

The Fall

3 Now the serpent was more crafty than any of the wild animals the Lord God had made. He said to the woman, “Did God really say, ‘You must not eat from any tree in the garden’?”

2 The woman said to the serpent, “We may eat fruit from the trees in the garden, 3 but God did say, ‘You must not eat fruit from the tree that is in the middle of the garden, and you must not touch it, or you will die.’”

4 “You will not certainly die,” the serpent said to the woman. 5 “For God knows that when you eat from it your eyes will be opened, and you will be like God, knowing good and evil.”

6 When the woman saw that the fruit of the tree was good for food and pleasing to the eye, and also desirable for gaining wisdom, she took some and ate it. She also gave some to her husband, who was with her, and he ate it. 7 Then the eyes of both of them were opened, and they realized they were naked; so they sewed fig leaves together and made coverings for themselves.

8 Then the man and his wife heard the sound of the Lord God as he was walking in the garden in the cool of the day, and they hid from the Lord God among the trees of the garden. 9 But the Lord God called to the man, “Where are you?”

10 He answered, “I heard you in the garden, and I was afraid because I was naked; so I hid.”

11 And he said, “Who told you that you were naked? Have you eaten from the tree that I commanded you not to eat from?”

12 The man said, “The woman you put here with me—she gave me some fruit from the tree, and I ate it.”

13 Then the Lord God said to the woman, “What is this you have done?”

The woman said, “The serpent deceived me, and I ate.”

14 So the Lord God said to the serpent, “Because you have done this,

“Cursed are you above all livestock
and all wild animals!
You will crawl on your belly
and you will eat dust
all the days of your life.
15
And I will put enmity
between you and the woman,
and between your offspring[a] and hers;
he will crush your head,
and you will strike his heel.”

16 To the woman he said,

“I will make your pains in childbearing very severe;
with painful labor you will give birth to children.
Your desire will be for your husband,
and he will rule over you.”

17 To Adam he said, “Because you listened to your wife and ate fruit from the tree about which I commanded you, ‘You must not eat from it,’

“Cursed is the ground because of you;
through painful toil you will eat food from it
all the days of your life.
18
It will produce thorns and thistles for you,
and you will eat the plants of the field.
19
By the sweat of your brow
you will eat your food
until you return to the ground,
since from it you were taken;
for dust you are
and to dust you will return.”

20 Adam[c] named his wife Eve,[d] because she would become the mother of all the living.

21 The Lord God made garments of skin for Adam and his wife and clothed them. 22 And the Lord God said, “The man has now become like one of us, knowing good and evil. He must not be allowed to reach out his hand and take also from the tree of life and eat, and live forever.” 23 So the Lord God banished him from the Garden of Eden to work the ground from which he had been taken. 24 After he drove the man out, he placed on the east side[e] of the Garden of Eden cherubim and a flaming sword flashing back and forth to guard the way to the tree of life.