An excellent friend of mine has been fielding job offers from several fantastic companies. While her work ethic, team expertise, and mad computing skills no doubt have much to do with her employability, she attributes her plethora of choices to having a strong Job Interview Theme Song. Her theme song is Cake’s "Short Skirt/Long Jacket." I think you’ll agree with me that this is an awesome choice. (UPDATE: I should have made clear that you really do want to click that link for the Cake song. It goes to one of the most entertaining videos I’ve seen in a while. (No rickroll, trust me.))
I’m self-employed and don’t require a theme song for job acquisition purposes, but I do need one for pretty much every other aspect of life. Especially meetings with prospective clients, and social events where I don’t know anyone. Fortunately, I have one: "Invincible" by OK Go. That’s the video above. 
Of course OK Go are my close personal friends (not really), but I knew this song was mine when I heard the lines "When they finally come to destroy the Earth, they’ll have to go through you first. I bet they won’t be expecting that." How could this not be my Theme Song?
I need some kind of device that can sense when my confidence is flagging and that can begin playing my Theme Song, preferably directly into my brain so only I can hear it and respond. In the absence of such a device, I cue up the song on my iPod before I back out of the garage.
A theme song that you play to yourself might seem a paltry means of building inner courage, but I assure you it works astonishingly well.
Right now, I think maybe the Pittsburgh Penguins need a theme song. I’d offer them mine — a "thousand Fahrenheit hot metal lights behind your eyes" would be a great help on both offense and defense, wouldn’t it? — but maybe there’s a better option. What should it be?
And while we’re discussing it: What’s your Theme Song?