What one song...?

What one song would you want to play every time a new thread comes up asking what one song you'd want playing at a specific event in life?

Mine would have to be:

"Here It Goes Again" - OK Go

transformers theme song..

sorry im in love with the transformers movie now that ive seen it 2 days ago..that movie was so awesome..i seen it once at the theatre, once on my computer, and im seeing it again when its out in imax..then when its out im buying it on blu ray for ps3. :D