The saddest of the sad songs - Slobberbone - Josephine. There really isn't another song that I've found that makes me feel the loss of a woman or the pain of never getting a chance. It's really well put together. I could get face down drunk and listen to this song for hours...in fact...I have.
The other one that gets me is this self-inflective Seven Mary Three song called Southwestern State. It's about betraying your own promises, but not the promises you've made other people - but the one's you've made for yourself.
Here's your overdose song.
More for ya - Sufjan Stevens - The Dress Looks Nice on You (my favorite train or rainy day in the car song of all time)
The ultimate stomach puncher - Everyone loves Mad World
The other sweet chin kicker - Another dead to early singer