Puff the Magic Dragon definitely - although my friends all think I'm mad :-)
Hobo's Lullaby
Streets of London
Patriot Game
Donna Donna
Hallelujah - the Leonard Cohen, Jeff Buckley and Rufus Wainwright versions... it's an amazing song!
Tears in Heaven - Clapton
Lara's Theme
Love Story
Send in the Clowns - just the tune, I guess.
Someday I'll fly away - from Moulin Rouge
Last Kiss
Arms of an Angel and When She Loved Me - Sarah McLachlan
Bridge over troubled water
Plaisir D'Amour - any version... but maybe, especially Joan Baez.
River in the Pines
Norah Jones always makes me feel sad.