So,
lanning is writing this Sherlock/John story backwards. Which means it's a WIP, but that doesn't really matter, since the first part is the last part. Umm, you'll see what I mean. This is the ending. This is the beginning. But read the end first.
fleshflutter wrote an awesome Sam/Dean BigBang fic which is just agonizing, in the best possible way.
de_nugis also has this wonderful bit of Sam/Dean angsty schmoop.
Edit: Major story spoilers in LJ comments.
Edit: Major story spoilers in LJ comments.