The penultimate episode of Stargate: Atlantis revolved rather heavily around Johnny Cash's "Solitary Man," both literally - as we see in the clip - and thematically, in that Shep is isolated from everyone around him in this iteration of his life.
A cover of Neil Diamond's 1966 hit, Johnny and Rick Rubin bring a bleak and haunting feel to it. And of course it's really cool when the A-10 Warthogs roll in...
and if that doesn't work, go here http://www.youtube.com/watch?v=CBGWk_qm-z4
That's Tom Petty on the backing vocals, by the way.