Well, from this list I picked "You Say You Don't Love Me"
I think many would pick "I'm Playing Easy to Get" if it were offered. It was played in concert in LA before the BBC radio session. While that radio version is available on various bootlegs, it was never properly released so I think it would count on this poll.
Speaking of that song, I'd love to know why he never took it any further than he did. GREAT song? No. GOOD song? Certainly. I would love to hear a polished version of it.