Everyone in baseball RPF fandom is familiar with candle_beck's writing, and it would be easy to just cherry-pick fics off her masterlist, but I'm going to start off by giving some under-appreciated writers some love.

Fandom: BASEBALL RPF
Pairing: Russ Adams/Aaron Hill
Length: 16,034
Author on LJ: instrumentality
Author Website: instrumentality's fic at The Boys of Summer
Why this must be read: I love the concept of the bildungsroman. Coming-of-age tales are perhaps my favorite type of fiction; I read two copies of Catcher in the Rye to oblivion in high school. I especially love baseball coming-of-age tales, and instrumentality has written exactly that. Despite the fact this is fan fiction, the story feels full and real, complex and layered. The characters are multidimensional and feel realistic, and the resolution to the story isn’t neat or pat. There aren’t any easy answers in real life, and To the End (of the Beginning) isn’t an easy story. Happy endings aren’t always what you think they’re going to be. The fact that instrumentality can take a familiar trope - star-cross’d lovers - and use it to craft a compelling and satisfying story is a testament to her skills as a writer.

( Excerpt )

To the End (of the Beginning)

Fandom: BAND OF BROTHERS
Pairing: ensemble gen
Length: 50 sentences
Author on LJ: falseeyelashes
Author Website: LJ fic tag
Why this must be read: Written in the familiar style of 50 prompts, one sentence per prompt, except the prompts really don't matter here. The author does a fantastic job of summing up everything heartbreaking and wonderful about the show, and the non-linear, fractured storytelling imposed by the style perfectly captures the splintering chaos of warfare. Just beautiful.

Bravery can be realized in the strangest of moments, almost as though by accident – the unfurling of a parachute, the endless rat-a-tat-tat from a machine gunner, the snap of a branch in the pale shadows of the moonlight, the exploding shell from behind, the sight of blood, the slip of it, the taste, the blood, yes, the blood, the –

Guarnere’s hands latch beneath Toye’s arms and he pulls, hard.

and chaos is luck

Hey there :)
I apologise for delay in delivering the goods- the last week will probably stay in my memory as The Worst Attack of RL in the History of My Short Life.
TWARLHoMSL.
Well, anyway... here we go:

Fandom: Lord of The Rings
Pairing: gen
Length: Long (1 123 KB, which is 662 pages in Word... etc. ;)
Author on LJ: I don't think she has one
Author Website: @ FF.net
Why this must be read:

This is a part of the series (it's the third piece actually) focusing on Legolas and Aragorn's friendship in their merry days before the Quest. This does not however mean that you need to read the previous stories from the series to understand this one- there're some allusions made, aye, but you are perfectly able to deduce and understand their meaning. I, for example, hadn't had even a glimple of one single line from the first and second fic before I stumbled upon To Walk in Night, and it didn't spoil my enjoyment in any way while reading.
Nili managed to do something that less and less (even gifted) authors of fanfiction manage recently: she has a plot. And amazing one at that. I adore the way she combines great humour (I was honestly dying from laughter during the first few pages, she enchanted me so strongly) and angst (also very well done, well managed and well justified ;P ).
Another point why this piece is so exceptional? Good original characters. They are thrilling- and they are very much alive, with personalities, background, ambitions, thoughts of their own, reasoning- they really fit into the canon, actually.
What else do we have?
Hm. "Good" villains? Check. (good, as you're most likely aware, is a matter of perspective)
The last thing I wanted to point out is the way no character is treated in a shallow way. The story's main focus remains Legolas and Aragorn, however we see much of Glorfindel, the twins, and beforementioned OCs (the fact which will not worry you- I am usually very wary of any Original Characters, but I fell in love with Nili's creations instantly.)

( Summary& Excerpt )

Link: To Walk in Night @ff.net

Fandom: MARVEL COMICS
Pairing: Steve/Tony
Length: 3,240 words
Author on LJ: jwaneeta
Author Website: Unknown

Why this must be read: Sexbots.

The Wages of Sin