Snips and Snails and Demon Tails
Set around 10x2/10x3, with some changes. After Sam captures Demon Dean, he calls Cas for help. Sam is leaning towards trying the new cleansing exorcism they discovered, but Cas fears that may have unforeseen results, given the Mark of Cain and Dean being a Knight of Hell, instead of a regular demon. Fortunately, Cas has another idea. (Hint: It involves sex.)
Dean isn't anywhere near as cold & uncaring in this as he was as a demon on the show. In this, he figured Sam could get away from Cole without his help (he did, after all) and he never tried to kill Sam. While I did have him kill the guy who put a hit out on his cheating wife, Dean feels bad about it. Oh yeah, and Cas left that Hannah broad to help Dean. This is actually a lot fluffier than I originally intended, lol. I have a sequel planned, but I'm not sure if it'll turn into a series or not, yet.
*Update -- includes a couple photos.