I incline toward the older, unconventionally attractive, and damaged characters, which means the relationships are often flawed and morally ambiguous. I also like stories about marginal people finding ways to love and be loved, even if the arrangements they enter into look undesirable to outsiders. I suppose that might serve as a content warning for the recs that follow. I adore most of these stories, even if they're not beyond reproach on a stylistic level.
<a href="http://archiveofourown.org/works/3860239">Night Watch</a> by mia_ugly - Snape/Harry, 18K words. Harry is imprisoned by Voldemort, and Snape is assigned the night shift to guard him. Poetic, somewhat bleak, beautiful, ultimately hopeful.
The connection between Harry and Voldemort is stronger than anyone realized. It is decided; the boy must be watched.
<a href="https://www.fanfiction.net/s/2712814/1/So-Lonely-Without-Me">So Lonely Without Me</a> by calligraphy, Snape/Harry, 41K words. Posted in 2005. Harry and Snape are sequestered in a room alone, waiting for Dumbledore to summon them back. Time passes, and their relationship changes. Funny, poignant, compulsive reading. One of the fics that sucked me into fandom.
Two men, two rooms, a war.
< href="http://archiveofourown.org/works/1130477">Going Concern</a> by crystal usagi - Snape/Harry, 27K words. Notable for the charm of the business partnership amongst the Trio and a compassionate rendering of the break-up of Harry and Ginny's marriage.
Tired of the work they are doing, Harry, Ron, and Hermione take over a small business together, running a magical antiques shop. When his marriage begins to fall apart, Harry turns to an unlikely confidant.
<a href="http://archiveofourown.org/works/495754">"Sod Off" Means "I Love You"</a> by anguis_1 - Severus Snape/Millicent Bulstrode/Dennis Creevey, 6K words. Forgotten, unwanted, overlooked people who create a fragile sort of relationship. Echoes of found family and slightly grotesque eroticism.
It begins and ends with the camera. Snapshots of life, and the living thereof.
<a href="http://archiveofourown.org/works/500220">Fair Is Fair, and Life Is Not (Though Tea Helps an Awful Lot)</a> by anguis_1 - Filius Flitwick/Pomona Sprout, 5K words. Charming and warm, a completely lovely slow development.
Although their students might sometimes be oblivious to it, teachers have lives, too. Fertilized with dung and watered with tea, Filius Flitwick and Pomona Sprout cultivate a love slowly bubbling along behind the scenes.
<a href="http://archiveofourown.org/works/317755">Father to the Man</a> by delphi - Severus Snape/Argus Filch, 20K words. A brilliant, funny fic with painful moments and an upbeat ending. Young Professor Snape botches a spell and summons his five-year-old self into the present day. Filch the caretaker takes care of them both.
A restricted spell goes awry, and Severus Snape is left scrambling to cover his tracks. Meanwhile, Argus Filch turns out to be surprisingly good with small children, the nature of time is proven to be fiddly and anyone's guess, and (at least one) Severus gets a second chance at life.
<a href="http://archiveofourown.org/series/49532">Fantastic Beasts series</a> by delphi - Silvanus Kettleburn/Severus Snape, 34K words. Wonderful, gradual, intelligent evolution of a relationship between a dandyish, scientifically minded professor with prosthetic limbs and a bereaved, taciturn young Snape. Still a WiP, with 12 installments so far.
<a href="http://hoggywartyxmas.livejournal.com/56425.html">We'll Take a Cup of Kindness Yet</a> by dueltastic - Aberforth Dumbledore/Minerva McGonagall/Severus Snape, 20K words. Witty, sharp, smart, and brusquely compassionate, with a fantastic Aberforth POV, "Yeah?" said Aberforth. "What's Christmas ever done to you? Shat glitter in your cornflakes and made you wear the little paper hat in the cracker?"
<a href="http://archiveofourown.org/works/1104139">Night-blooming heartsease<a/> by julad. Severus Snape/Neville Longbottom, 32K words. Yes, you read the pairing right. This fic has magic, battles, high emotions, inventiveness, and tremendous heart. Neville's POV is perfect, and - well, this is the magic of fanfiction. This writer makes you believe in the relationship. A desert-island keeper for me.
Snape swooped around the room like a giant bat, adding ingredients to some cauldrons and stirring others. Then he stopped and tapped his wand against the benchtop impatiently. "Well? What is so important that I must risk a vital brew of Animaserum by having you in the room with it?"
His tongue was so dry, he didn't know how he would ever get the words out. "Heartsease, Professor." There, that wasn't so hard. He took a deep breath. Dementors were worse, surely.
That's enough to be getting on with, I think.