In other words, what's a song that you can listen 100 times back to back and still enjoy it. For me, it's Door by Caroline Polachek; the song manages to be the perfect balance between catchiness and entrancement to not get tiring.
Dark Star by Grateful Dead
Every instance has its own flavor, and beautiful explorations based on how the band feels on that night. I've yet to hear a rendition of it that I didn't love.