Okay, this one isn't as niche as much as it's overlooked. Going to have misc recommendations on primarily horror games.

Penumbra Collector's Pack - $2.49
Made by the creators of Amnesia: The Dark Descent and SOMA, it's 3 games in one for the Penumbra series (Overture, Black Plague, Requiem, in that order). While their younger brothers Amnesia and SOMA get talked about a lot more, I've always felt the Penumbra games were more playfully fun and tenser experiences.
Penumbra stars a man going to Greenland after receiving a letter from his dad, who has been missing for years. The letter tells him to forget about him and order an entrance to a mine to be blown up. Our character, caught by left field, decides to instead first investigate said mines. And thus the apt, 'dark descent' begins!
Penumbra's story is told in three games, though maybe really only two (the third game, Requiem, was an expansion for Black Plague and has a minimal story and is completely puzzle-focused). Overture and Black Plague however takes us into the first-person mostly defenseless horror games Frictional has become known for, but honestly I've found it to be their best execution on the idea. Instead of becoming more a hide'n'seek simulator, you're given tools and environmental aid to tackle what the game throws at you; from beef jerky you can lay down to distract dog enemies, to boulders to push to block tunnels, pipes spewing steam, upper and lower pathways, and more. The monsters also come in a variety in Overture, and the game mixes itself often with different thematic rooms and areas, some thought-provoking puzzles, and strange moments and scare scenes. In Black Plague, there's also some fun surreal and illusion elements as you seem to be losing your mind and a strange, colorful character in your head talks and consults with you while messing with your perception.
I mainly recommend it as I think it's far overlooked to its brothers, and I honestly like them quite a bit. It feels a bit more 'gamey' than either Amnesia or SOMA, but I found it also more 'fun', more varied, and and honesrtly it scared me overall a bit more. With the larger variety it kept me guessing a lot more and doesn't become too predictable, a flaw I had with Amnesia later in. If for some reason you haven't played it and don't mind a first-person horror game, or especially if you liked Amnesia, maybe SOMA, I'd recommend it. Also, it's two and a half dollars for two and a half games.
Some screens:
Again, hope some find these useful and will be posting more. Mobile makes it slow for me.