'when I was your man', by Bruno mars. It's a song about how he has regrets because he didn't pay attention to this girl and do her favors. It was almost completely similar to a situation I was in. This high school sophomore girl was into me, and I kind of ignored her. I guess she got hurt, and now she doesn't try to talk to me. I regret not speaking to her and I feel bad. So every time I listen to the song it reminds me of her. So that's why when a girl try's to get your attention, don't hesitate to talk to her. Hurting their feelings is a very bitter feeling.
Love Theme (I forget the composer) Living With Determination (sad in context, composed by Shoji Meguro, I think) Debriefing (MGS3 soundtrack) Pretty much every song in MGS4 that plays during a cutscene, which is pretty much all of them.