I love reading Sam and Dean when they were really, really young (i.e. Dean's no older than 15 or 16). Cutesy fics just showing the relationship between them with Dean raising Sam is good, but I have a sick thing for them being together sexually when they were really young (Sam: 5 and Dean: 9).
Bonus bonus bonus if John's involved in the extreme underage sex/relationship. If anyone knows any stories like this, mind sending me in the right direction?
If not, just regular weechester stories are more than good.