Remix: This Gift Or This Curse (The Reliable Remix) [Sam/Dean, 100 words, rated R], by sororcula
Dean knows Sam. He knows the pale color of his face when the blood's drained out because it's flowing out of a bullet wound in his shoulder, and he knows the way Sam moves in sync with him when they're hunting.
He knows Sam's taste and Sam's sounds and Sam's smell and how strong Sam's hands are when he grips onto Dean's body and how deep Sam's voice goes in a growl when he can't speak anymore, he's so far gone.
He knows everything Sam can do and what Sam will never do. Who Sam will never be. He knows.