Too many diverse songs for me to pick one. Would depend on my mood.
Best album, depending on my mood, would be Sgt. Peppers, or Abbey Road. Abbey Road, as it has a poignant meaning behind it.
When I see "Let it be" and "Revolution" picked, I have to ask, "Which Beatle version?". Then follow with, "How many know there are two distinct cuts of each of those songs?".