BuddyTV have listed their Top 8 of '08: Most Shocking Moments of the Year:
#2 Dean is Touched by an Angel
There were so many shocking things that happened on Supernatural this year. Sure, it was shocking at the end of last season when the Hell Hounds finally caught up to Dean, and he really was sent to Hell, but I think few people anticipated that it would be an honest-to-goodness angel – and a kick-ass one, at that – to be the one to rescue him from the pit. Castiel revealing his wings, along with the message that God has plans for Dean Winchester, leads Supernatural in an entirely different direction, and one that we're sure all the fans can't wait to follow.
Source: BuddyTV.