Specific-Fic: Ssn2 Destiel AR
This one is a longer fic (possibly a big bang?) ssn2 AR where the angels have gone back in time to basically kidnap Dean's soul for later use. It starts out with a car crash where Dean dies, and a Reaper hired by Michael&Co. tries to kidnap Dean's soul, but Castiel shows up in time to save him. Then basically the fic is Dean and Castiel fleeing from the angels, with an appearance by Raphael leading to some bamf!Dean protecting hurt!Castiel followed by some good ol' fashioned h/c, and at the end they change the future such that when Dean is returned to his body, Castiel ceases to exist and Dean struggles to not but eventually does forget Castiel because of this, followed by Castiel actually surviving/existing and calling Dean so they meet up and have a happy ending.
This fic is one of my absolute favourites, so any help finding it would be rewarded with a million virtual hugs and cookies!