My number one favorite would be While My Guitar Gently Weeps, but since it is my favorite by sooooooo little I feel obligated to add these:

Revolution
Come Together
Yesterday
Help!
Ticket To Ride
The Night Before
Wait
Let it Be
Penny Lane
Strawberry Fields Forever
I Wanna Hold Your Hand
I Saw Her Standing There
Eleanor Rigby
A Day in the Life
With a Little Help From my Friends
Michelle
In My Life
Norwegian Wood
She Loves You
All You Need Is Love
Sexy Sadie
Happiness Is a Warm Gun
Hey Jude

These are my *current* favorite Beatles songs.