Definately the intro to the Let it be version of "I've got a feeling". I've never heard that intro duplicated sucessfully. I also love the "I've got a feeling..A feeling deep inside..oh yeah..oh yeah..Dats right!".(Paul McCartney is so cool lol) Another part I love is how he shouts "Yeah!!" throughout the song..makes you want shout with him. I love that short guitar solo in the middle of the song and the bass in the whole song.
I love the blaring intro to "Helter Skelter"...you know exactly what song it is when it starts. The harmony vocals by John and George are suberb "Da Da Da Da!" and the "Aaah!!", no one will ever be able to do the harmony vocals as superb as them...no one. I love when Ringo joins on the drums on 0:06 of the song, and of course Ringo's "I've got blisters on my fingers!!"
I'll post more when I can think of some lol