My ABCs of sad songs

Always on My Mind - Willie Nelson - 1982

Come Away With - Norah Jones - 2003

Do What You Have to Do - Sarah McLachlan

Eddie Vedder - Without You

Forever Love - Reba McEntire

Gilbert, Doug - Crystal Gale's 'Til I Can Gain Control Again - 1984

How Far - Martina McBride - 2004

I've Never Been to Me - Charlene - 1982

Key Largo - Bertie Higgins - 1982

Landslide - Stevie Nicks

My One True Friend - Bette Midler

"Nothing compares to you" Sinead O'connor

Oasis - "Sad Song"

"Queen of My Heart" by Hank Williams, Jr.

Remember When it Rained" by Josh Groban

"Tell Me a Lie" - Janie Fricke
Underwood, Carrie: "Jesus Take the Wheel"

Van Morrison's "My Lonely Sad Eyes"

Whiskey Lullaby by Brad Paisley, Alison Krauss

X, as in "Why" by Annie LennoX :) 

You Had Me From Hello - Kenny Chesney - my favorite video? Jag clips
Zach Sobiech's "Clouds" is the most uplifting "sad" song I've ever heard.
http://www.youtube.com/watch?v=sDC97j6lfyc