I'm not as eloquent as Samsarapine when it comes to reccing fics. She has such a way with words that make you just wanna go check it out. Nonetheless I'm gonna try cos they are really, really good. These few fics actually made my shitty week bearable.
Here goes :
Merely Passing Strangers by Hallidae
The Artificial Intelligence Principle series by Hallidae
Pieces For The Wrong Puzzle by Hallidae
The Flashbulb Shatters by Hallidae
My 2 cents on Hallidae's fics - Author claims that some of the fics are prompts from the kinkmeme but I think the author did a great job with the prompts. He/She owned the story. Hey, you can give me all the best prompts and I'd still turn in shit so I really think the author deserves all the credit. The stories are mostly AU, and the style of writing is consistent and catches your attention. I was totally enthralled with the storyline and plot - it was really refreshing. Specifically to the AI series, I think that I may have read or seen bits and pieces of it from other fics or parts of some movie (I may be wrong but it just seems kind of familiar) but I am amazed how the author had woven all of it into one story credibly and seamlessly. The Flashbulb Shatters is another amazing AU. I wish I can explain better how amazing these fics are without giving out spoilers. I would summarise it as totally unexpected but immensely satisfying.
Love is Like.... by pantswarrior
An Honest Answer Is Like A Kiss On The Lips by pantswarrior & akatonbo
My 2 cents on pantswarrior's fics - You can say the author's fics are AU but I think canon divergence suits it better. The author weaves a story arc into the original canon and it fits in perfectly. Please be assured that the author does not dwell on canon, so you don't have to worry about reading repeats of what you already know. I really liked Love is Like.... It tells of Kotetsu's screw-up despite his good intentions.My heart twinges for Barnaby in almost every chapter - it's just that good.
All the fics above are BarnarbyXKotetsu centric. These fics have really impressed and touched me and I felt the authors deserve more recognition and readership in AO3 - which may not be a really popular place seeing how young this site is.
So if you have not already read them, please do give them a try. I can almost guarantee that you will not regret it. ^_^
P/S All the fics above are complete so you don't have to worry about being left high and dry.