My first pass top-of-mind:

Let it Be-The Beatles
God Bless the Child-Billie Holliday
Exit Song (for a film)-Radiohead
Rhapsody in Blue-Gershwin
Bridge Over Troubled Water-Simon & Garfunkel

Alan and ZoeGirl:
My son and husband LOVE "Hurt" by Johnny Cash and they played it several times this past holiday so it's very fresh in my mind. It's a little depressing to me, but it is a beautiful song