Hi there! I'm bistokids, and I'll be at the wheel of the Life on Mars van for the month of September. I'm a confirmed slasher, and 'ship Sam/Gene as my OTP, so my recs will probably be weighted in that direction - but I'll try and include a few gen entries, and maybe even the odd other pairing, just for fairness!
So, here goes with rec one...

Fandom: LIFE ON MARS
Pairing: Sam Tyler/Gene Hunt; Gene Hunt/OMC (non-con)
Length: Part 1 - 1,100 words; Part 2 - 13,500 words
Author on LJ: elfinessy
Author Website: Elfin's Life on Mars archive
Why this must be read:
In a nutshell, because it's Elfin. This author has done more to draw readers into the fandom than any other, through her comprehensive and user-friendly website. And her thoughtful characterisation, rounded plots and vivid storytelling skills place her up with the very best the fandom has to offer.

'Polar' is where my own Life on Mars fanfiction journey started, and it's a story I regularly revisit. It's in two parts - the first is short and packs a hell of a punch. It contains a brutal and graphic description of the rape of a main character by a canon villain - if you find this too squicky, it's not necessary to read part 1 for an understanding of the story as a whole. (I've included links to both parts, so take your pick).

Part two is much longer, and deals with the aftermath of the attack, the development of the professional and personal relationship between Sam and Gene, and Sam's own feelings on how this event impacts on his carefully constructed perceptions of Gene and 1973 at large. Inevitably, there's a decided element of h/c, but Elfin's complex characterisation maintains the integrity of the canon characters, while rounding and softening them somewhat without mawkishness or excessive sentimentality.

Part One here
Part Two here

Fandom: STARGATE SG-1
Pairing: Cameron/various - gen, slash, het
Length: one-shot
Author on LJ: helens78
Author Website: HelensFic
Why this must be read:
Written for the Five things that will break Cam, in the end prompt at sg1_five_things. I love each of these. Cameron is pared down to the bone in these. Whole worlds built in short little snippets. Great storytelling. I cannot decide which one hurts most because they all do. Adored them all. Poor Cam.

The Bright And Hollow Sky

Fandom: House, M.D
Pairing: Amber/Thirteen
Author on LJ: maypirate
Author Website: @ LJ

Why this must be read:

Thirteen won. This one is set after 4.9, and features a fabulous Amber: unhappy, angry, trying *so* hard not to care. And, of course, hating Thirteen.

"Could be that I just like being a bitch." And maybe that's true. Maybe it's all just about notches in the bedpost, scars across her heart, titles won and lost in every right and wrong answer. If you never let them know you keep track and still care, they can't hurt you where it counts.

"Sure. I'll buy that." Thirteen quirks up the side of her mouth, half-smiling. "You know I'm kind of going to miss you."

"Aw, really?" She cocks her head to the side, making as condescending a pouting face as she can. "You think we could've grown into the bestest friends?"

"I think we could have been bestest enemies," Thirteen says.

I love this pairing, and this story captures it in its fabulous, hatesex glory.

The History of Being Wrong

Fandom: JUSTICE LEAGUE ANIMATED
Pairing/Characters: Lex Luthor, Mercy Graves, Braniac, Piper, Two-Face, Joker
Length: One-Shot
Author on LJ:
Author Website: ff.net account

Author Summary: They all have their niches, and they will always fill them. But if they didn’t, if they went outside those lines drawn in the sand…

Why this must be read: The best thing about comics is that there are good guys and bad guys, and the good guys always win, right? But what would have happened if the bad guys had acted just a little differently?

amarin_rose gives us five quick peeks into some 'what-if' situations. My favourites, personally, are the last two, simply because they're chillingly possible (even probable) in canon.

Find it here.