Alone - it's as indie as they come but shows what can be done with basic art and some well chosen stock sound effects to create a feeling of Isolation.
(Image added so people know which one as there are multiple games called Alone on steam)
Slayaway Camp - One of the best puzzle games I've ever played that adds mechanics as you go but never feels like it becomes stupidly impossible to work out. Also it has a slasher film style theme to it so if you like 80s style slasher films you'll likely enjoy the references and jokes.
A Robot Named Fight - A Roguelite Meteroidvania game. I don't think I should need to say much else.
Noir Syndrome - A Roguelite Detective game which sees you hunt down a serial killer, each time you play the clues and killer identity is procedurally generated as such.
Unrest - by an Indian indie studio it can best be described as a multiple choice adventure game where you follow multiple characters whose story all becomes part of the larger story of what is happening to the fantasy kingdom where the game is set.
Detective Grimoire - A point and click game from SFB games (you may have heard of their more popular title Snipper Clips). It's got great art style and a an enjoyable sense of humour. It felt like a far superior title than say Broken Age did and was made on a fraction of the budget. I will say the puzzles are a little on the easy side though.
Survivalist - A sort of Strategy sort of partially top down third person shooter game about surviving after the Zombie apocalypse. I'd say it should be up there as one of the best Zombie games around with a lot of freedom to tackle things how you like.