My favourite above all others is called "Repechage" por Fabula Rosa. It's a bit... sexy... But has a truly beautiful storyline about how the two come together.
I amor Drarry, Harmione, Sev/Hermione, Ron/Draco, and Remus/Sirius. But, much like LadyNottingham, my all time favorito is Severus/OFC :) (It's fun to write too!)