"Jesus, Take The Wheel". It's about a woman who's driving home for Christmas, with her kid in the backseat. Then she loses control of the wheel. It's depressing to say the least.
Though the song does have them both survive - the car just skids onto the shoulder and to a stop, and the woman vows to change her life (though it isn't really said exactly why she has regrets about it).
"Mama's Song" is another one — with the bittersweet, low-key instrumental backing as a key component.
Hell, pretty much any song involving God or her mother is gonna be emotional.