Breezeblocks by Alt-J. I listened to it over and over again last year when I was in a very depressed and negative state in my life. Also Love Don't Die by The Fray. No particular reason, no deep lyrics or angsty rock sound or something, I just happened to really like those songs at that time.
Listening to them just reminds of those heavy emotions, which is very unfortunate because I'd like to listen to those songs again without those bad memories.