The rooftop performance.
I'd designate "Don't Let Me Down," John's impassioned plea to Yoko, as the best song from the set. The Beatles actually played it twice, and in the version that's below John badly flubs the opening words of the second verse. We should be thankful he did because the moment that he and Paul share after the miscue is wonderful. Paul almost seems to walk John through the next line, and then the two exchange very knowing and genuine smiles. Coming amidst the band's protracted collapse, it's a reminder of the powerful bond that John and Paul had fostered over the years.
Finally, I'd be remiss to not quote John's parting shot: "I'd like to say thank you on behalf of the group and ourselves, and I hope we passed the audition." (Source: the link above.)
(If the video is removed, go here.)