This horror AU on Twitter is a must-read if you are a part of the fandom, and like reading fan-fictions. Not only is it well thought-out and well-written, but also leaves the readers with a lingering sense of unease and eeriness because of its ending. Just give it a read.
Not in this Lifetime by Sel. A twitter-fic that deals with human relationships and feelings with a very realistic approach, hitting home more often than one would expect.
Archive of Our Own
vonseal's works. From heart-fluttering fluff to gut-wrenching angst, they have everything. They're all very well written and thought-out, with extremely witty dialogue-writing. One of the standouts would be magic users, a series of fics about the Astro members as magic users in an Alternate Universe.