Probably due to the recent explosive manga chapters, there's been a corresponding explosion of excellent Ao no/Blue Exorcist short fics lately.
Terminus by Swift-Star9
Series: Blue Exorcist (Mangaverse, post-Chapter 96)
Rating: T/PG-13
Warnings: Violence, profanity
Location: Fanfiction.net
Status: Complete/Oneshot
Summary: He hated to lose.
Comments: Brotherly feels! After the latest manga chapters, I'm completely in Okumura brotherly feels mode, and this fanfic delivers. The opening is rocky, but, ah, the ending makes it all worth it. Which, of course, is what I'm hoping for with the manga canon too.
Brothers by I wrote once too
Series: Blue Exorcist (Implied manga setting around chapter 97, but could potentially be any continuity)
Rating: K+/PG
Warnings: Intense emotions (I'm not really sure why the author rated it T.)
Location: Fanfiction.net
Status: Complete/Oneshot
Summary: They were brothers, Rin and Yukio.
Comments: I don't usually pick the angstier fanfics, but this was such a perfect snapshot of Rin and Yukio's issues. It reminds me of the images from the second ender to the 2011 anime. Where Rin and Yukio are both reaching out yet never connecting until, finally, they're left facing away from each other. That's exactly how their relationship feels so often.
Joys in Growing Old by I wrote once too
Series: Blue Exorcist (Mangaverse, post-Aomori Arc)
Rating: K+/PG
Warnings: Mild profanity
Location: Fanfiction.net
Status: Complete/Oneshot
Summary: A mirror is the most telling, after all.
Comments: Just a nice little look at Shura post-Aomori, realizing she actually has a future. And, a nice reminder that, more and more, the theme of this series seems to be escaping the chains of the past. Rin and Yukio have, one way and another, helped the rest of the cast do that. I suspect, I hope it will be time for them to be repaid in kind soon.
Attitude Adjustment by Koi Lungfish
Series: Transformers (G1 Continuity, Between the Series and 1986 Movie)
Rating: K+/PG
Warnings: None.
Location: Fanfiction.net
Status: Complete/Oneshot
Summary: Hot Rod meets the Dinobots for the first time.
Comments: And, alongside all the AnE brotherly feels, I've been on a memory lane Transformers kick lately. For whatever reason, I remember the post-movie episodes and characters best and have a huge soft spot for the Dinobots and Hot Rod. ...Because Boisterous Bruisers and a troublemaking kid with a heart of gold? Mmm, yeah. Those are my character types. And, watching Hot Rod's good deed get him swamped by overly-enthusiastic Dinobots is both sweet and hilarious.