The songs throughout the series, as performed by The Valli Girls, are both awesome and heartwarming.
The opening/ending theme, "It's A Hair Thing," describing the premise of the show and the appeal of magic.
"Best Friends for Life" is this and a Heartwarming Moment.
"The Power of Five" is a rockin' song about how the girls use the Power of Five to defeat evil.
The song heard at the beginning of the Middle Ages story arc, describing Simon's plan to turn back time.
In "New Girl In Town", the song when Garnet speeds off with Amethyst and friends. It reveals a bit ahead of time that Garnet is Simon in disguise.
The Trollhiti song is one of the few songs to be played fully in an episode, with little talking over it.
The "Best Friends for Life" reprise in the series finale gives the show a sense of closure, and also has the second verses not heard in the first music video.
The Italian theme song is completely different from the English one, but is also completely awesome.