Dean's an incubus, well, sort of...
Catenae Cupiditatis by leonidasden - wincest, first time, Dean as an incubus (sort of).
To get Dean out of his deal, Sam makes a deal with a succubus for Dean to "feed" on her behalf once a month. Angst, sex, more angst, and angsty wincest ensues. With added awesome!Bobby for the win. :D
This story is incredible. Well written, great characterisation, beautiful detail, and awesome lines, all come together to weave a beautiful, tragic, yet hopeful story which, while incredibly hot, actually isn't really about the sex, so much as being about the boys' deep, intense, *too-much* love for each other and just exactly how far they would go and what they would sacrifice to save each other.
But what else would one expect from leonidaslion?