I think "I Want You" is a early marker towards Lennon's solo output, filtered through the Beatles studio finesse.  Brilliant, ground-breaking, and actually a pretty sweet jam-- something you don't usually associate with the Beatles.

I really consider "Maxwell's Silver Hammer" the worst thing they released, Lennon's "Please proceed, Governor" moment towards Paul McCartney.

"I'm OMAC!  Evacuate this section!  I'm going to destroy it!"