The song that I most identify with is definitely Breathe Me by Sia.
Relationship song...don't have a mutual one, but I sang him Ingrid Michaelson's "The Way I Am", which I think is relevant. I'm not really into the super lovey dovey "omg they're playing our song honey!!!11 let's embrace or slow dance cheezily" type thing. "The Way I Am" is jazzy pop, simple, endearing but not intense or tear-jerking. Not a ballad. Not really...sentimental, it just happens to be applicable.