I think the Beatles' best song was Revolution (the single version; an incredibly powerful B-side to Hey Jude that I am old enough to remember my brother purchasing new at the record store). The Beatles did a great semi-live version of it on David Frost's U.K. show (which aired on The Smothers Brothers Comedy Hour in the states). Nothing I could wax lyrical about it would rival enjoying it for yourself here.
Revolution never appeared on an original album. Two songs on the classic White Album bore similar names - Revolution 1 and Revolution 9. Revolution 1 was the slower, original version of the single, but Revolution 9 - well, that's a story for another time.
A bootleg version of "Revolution 1" was recently leaked to the internet - a full 10:00 recording which contains elements from "Revolution 9". It was the original intention of how both songs were to be presented on the album, and it can be heard here.