To narrow down all my favorite songs into 1 favorite song...whew, but the winner is:
A Pirate Looks @ Forty by Jimmy Buffett
This song spoke to me the first time I heard it. I'm a child of the water and the lyrics "Mother, mother ocean, I have heard you call. Wanted to sail upon your waters since I was three feet tall." When both of my nieces were born, I would sing this song to them as I rocked them to sleep.
Here's Jimmy singing the song with Zac Brown on CMT's Crossroads