Jan Hammer did some wonderful work on Miami Vice, and it is difficult to choose just one from three years worth of episodes (they recycled his work once he left the show after I think Season Three). But if I have to pick, it would have to be what has been called "Dorothy's Theme." It's used effectively in so many scenes, like here (from "Milk Run"):
But here's the original (sorry about the quality, but I have no control over it because Youtube):
It's perfect for Dorothy's character (and any scene that is about innocence lost), and it makes me miss this series all the more. Well, the first three seasons, anyway.