Today my answer is Mother Nature’s Son.
Revolver was the "transition" album. The move from the moptops to Sgt. Pepper. LSD, the '60's culture around them, George started into Indian music, etc. Perhaps the most diverse collection of songs ever, by anyone.
"Tomorrow Never Knows" was recorded in April of 1966. How did they go from "Help!" to "Tomorrow Never Knows" in 8 months? Astounding. And they were still performing in concert at this point, playing their oldies, and hating it. Last concert in August '66.
Here's a great video from PBS about the recording of "Tomorrow Never Knows":
walrus
If I'm not mistaken, "Tomorrow Never Knows" was the FIRST song recorded in the Revolver sessions (even though it appears as the last track on the LP). That blew me away when I first read that. To have created that at the beginning, it surely must have set the tone for the rest of the album.
Get Back is a song I always enjoy listening to, but another one that grabs me in a different way every time I hear it is The Word from Rubber Soul. That album was an amazing game changer when it came out. It was clear they had jumped to another level.