"If I Fell" from A Hard Day's Night, most particularly for the gorgeous harmonies and Lennon's nasal landing on "pain". A lovely little ballad, one you'd expect to have been written by McCartney, but actually one of Lennon's.
Whenever I hear "She Loves You", it takes me back to when I met my husband in 1963, so have very fond memories of it, although it's not particularly my favourite.
Gotta be "Within You Without You" by George Harrison.
Just about sums up that hippy era. Just listen to the words.
George playing the sitar is pretty awesome too.
I think that the Beatles are the only group where you can play 10 second intro`s of practically every one of their songs and you automatically know the lyrics that come next, even if you are not a fan of theirs.
They were brilliant.