I have a lot of recs, so I think it'll be best if you just go through the tags on my Delicious account. Ratings, seasons and appearing characters are all tagged, so you can choose which fics sound good to you.

- fics with hurt!Dean (https://delicious.com/hunenka/hurt!dean)

- casefics (https://delicious.com/hunenka/casefic)

- fics with the Mark of Cain (https://delicious.com/hunenka/mark!of!cain) (and if you don't mind self-recs, I wrote one short fic dealing with the Mark's effects on Dean here (http://archiveofourown.org/works/1515515).)