>>1900652I was about to write a post very similar to this one.
As somebody who has trawled through the hellscape of FFN's MGLN archives, I firmly second When I Think Of Flying. The author has since gone on to write similarly excellent Korrasami on AO3, but never crossposted WITOF there. A pity, since it is really good.
Extrinsical is the one who does most of the weird 'then they turned evil and killed each other' fics. Their writing style is interesting, but often dips into purple prose.
Game Theory is the technically best fic in the English-speaking fandom.
deathcurse's subaru/teana stuff is my favourite amidst the scant pickings. The 1st story in their series is rough around the edges, but I enjoy how the sequels deal with Subaru and Teana's many emotional hangups. It's a pet peeve of mine when people rush characters together without thought for their nuances of character.
Friends With Benefits is a guilty pleasure of mine. I honestly forget how much fucking goes on in that fic, given that the first thing I remember when I think of it is Fate's perplexing inability to assemble Ikea furniture.
And...whoa, thanks for the rec; I'm the one who wrote the Subaru/Teana AU with the car. Sorry about all the spelling errors! I plan to update with more in-depth edits when I post the sequel.