Depends on my mood, but here are a few favorites:

Yesterday
You Know My Name, Look Up the Number
Back in the USSR
While my Guitar Gently Weeps
The Long and Winding Road
Help of my Friends

but my FAVORITE stanza is from Day in the Life....
Woke up, fell out of bed,
Dragged a comb across my head
Found my way downstairs and drank a cup,
And looking up I noticed I was late.
Found my coat and grabbed my hat
Made the bus in seconds flat
Found my way upstairs and had a smoke,
Somebody spoke and I went into a dream (ahhhh ahaha ahaaaaa)

I don't know why, its just FUN to sing along with that part!

Most of my favorites are from later in their career. I love anything by them really.