A little unrequited Lily/Snape, written when OOtP came out.
Professor Severus Snape did not like fresh air. His rooms and laboratory were in the dungeons; they were very clean, very orderly, warm and comfortable, with no windows and no outside air. The chill dank presence of ghosts and the curt gusts caused by his robes whipping around his legs as he strode through the corridors were the only breezes he tolerated to invade his space. A draft would be sealed with an irritated wand-wave as soon as it made itself felt. At the meals with the staff, he stayed only as long as necessary, frowning at the fresh air that blew in with the jabbering, excited students running in from outside for their meal. He wrapped himself in a cloak and a hat and withdrew into that cocoon at every Quidditch match. It was noticed, of course, and remarked upon - mostly by Gryffindors, but to them it was just another of that greasy git's oddities, another antisocial, batlike, cave-dweller fetish. He didn't care. He knew the image they had of him, and it suited him well. Their mockery was a thin disguise for fear, and he knew and understood fear. It was something he had control over, something he could hold in his hand and mold to his own purposes - instructional, these days. As good as any.
They could not know what fresh air was to him; they never understood that subtle difference between his impatient annoyance at their chatty exuberance and the wistful annoyance at the fresh air that gusted through the classroom and rippled the stack of papers on his desk when they piled in for class. They certainly could not know what flood of memories fresh air held; memories of the fiery-haired, fiery-tempered woman with the fiery intellect, with her head out of the window of the Hogwart's Express, singing an unidentifiable song into the wind; memories of sidelong looks at her hanging out of the window of her dorm, high above, grinning into the breeze, while he walked to the lake on a lazy spring day. And they would certainly not know of that silly game that day, the one that turned into a free-for-all game of tag; of running after her until they both collapsed on a grassy hillock, panting, and she turned her lovely smile at him and he...
The next time he saw her, she was wearing that smile at his side. /Potter's/. Sometimes, he feels that nothing he said would have made a difference. Butsometimes, he knows that he'll never know now. And so, when the spring air comes blowing through the open windows and doors of Hogwart's, drifting through the corridors, laden with the smell of grass and growing things and heartlifting hope, he closes himself into the dungeons, where fresh air never intrudes and he can, for a while, keep regret at bay.