Townes Van Zandt's Tecumseh Valley, and Steve Earle's tribute to Townes, Fort Worth Blues are grabbers. I also noticed several mentions of Gram Parson's songs or singing in this thread. Hot Burrito #1 definitely a heart-breaker, but his duet with Emmy Lou on the Louvin Bros' Sleepless Nights gets me everytime...especially the soul-harmony on "why did you go? why did you go? don't you know, don't you know I need you?"

The one I've given up on is I Come and Stand at every Door. I love the song, but I choke up about halfway through it.