These ones are definitely worth watching:
Song: "God is a girl" by Groove Coverage
Anime: Ah! My Goddess OVABelldandy is a god
Many different special effects and perfect timing. Scenes of other charas too, but mainly K1/Bell.
Song: "Million Tears" by Groove Coverage
Anime: Ah! My Goddess MovieAddict - Kara version
A Karaoke version of the song, with Bell as main singer. Nearly flawless lip-sync and incredible timing here too.