I find Castiel an amazing character. Beside the obvious amazing looks, his role is intriguing. Misha Collins plays Castiel so well, I couldn't imagine another actor for the angel.
Castiel is the one that saved Dean from Hell and soon after rebelled against the angels that were corrupted by Lucifer. He took the side of humans in the Apocalypse war, paid by death twice and lost his powers. Apparently he was revived by God and given his Grace back.
As a character he's so adorably oblivious and reacts so amuzingly to his surroundings.
Dedicated to Yours Truly because I know for sure she watches Supernatural and this baby can't exist undedicated XD