Paul,
I agree with your assessment of “I Ain’t The One.” “Free Bird” is essentially a great guitar duel preceded by four minutes of garbage.
From Zep IV, I would choose “When the Levee Breaks.”
Occasionally, one of those minor album tracks is rescued from obscurity. For example, the hit-filled Cars debut (essentially the Cars’ greatest hits) has a great track called “Moving In Stereo” that might have ended up lost in the shuffle. Fortunately for us all, Phoebe Cates rescued it.
