Dean: ESTP-hard core. He is a classic doer. Doesn't think of the consequences to his actions, ect. But he is fun loving, spontaneous, and good natured (also-I love him more than is OK for me to love a fictional character).
Sam: INFJ-strives to have a normal, orderly life, but his idealism, his loyalty toward Dean, and his caring for others makes him continue the Family Business. He also is surrounded by that INFJ tortured sad aura.
Castiel: ISTJ- talk about the Duty Fulfiller complex. Mind you, he did rebel, but that was after thousands of years of just doing what he was told.
Bobby: ISFJ-I say this because my dad is about that age and is a male isfj, and he really reminds me of him.
Women characters: non existent or not well thought out.