I read very little SPN (it's one of those fandoms where I enjoy canon, but don't feel a particular need for fic) but my all-time favorite SPN fic is this one which was rec'd to me by a friend awhile back:
It doesn't exactly fit all of your criteria, but like I said, it's the one *I* liked the best. Since you haven't seen the show ... one of the characters died at the beginning of Season 2, and the basic premise of this story is that a group of Goth teenagers conducting a pretend seance accidentally bring him back to life. I happen to be hugely fond of outsider POVs on events in canon, and this is a really fantastic example of that sort of story. It should be total crack, but instead it's totally engaging and convincing ... and completely gen.
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http://community.livejournal.com/spn_gen/322823.html
It doesn't exactly fit all of your criteria, but like I said, it's the one *I* liked the best. Since you haven't seen the show ... one of the characters died at the beginning of Season 2, and the basic premise of this story is that a group of Goth teenagers conducting a pretend seance accidentally bring him back to life. I happen to be hugely fond of outsider POVs on events in canon, and this is a really fantastic example of that sort of story. It should be total crack, but instead it's totally engaging and convincing ... and completely gen.