There should be six favorites, as it's a double album!
Here are my SIX, in no particular order:
While My Guitar Gently Weeps, Back In The USSR, Dear Prudence, Happiness Is A Warm Gun, and Long Long Long ... and ...
Oh yes ... how could I forget ... my sixth is Revolution 9. Seriously: as a musical collage (rather than a song), it is first rate. Would that some of McCartney's superficial tunes had been given the heave-ho (Martha My Dear, Rocky Raccoon), and good stuff like George's Not Guilty and John's Mary Jane inserted instead.