I love pretty much all of the songs from Bakemonogatari, Nisemonogatari, and the others. My favorite thing about them is that the openings are horribly misleading. They are all character intros so the show always seems so nice. The endings give you a better idea of how hectic and complicated the character relationships are.
staple stable - Chiwa Saito
Kimi no Shiranai Monogatari - supercell ft. Gazelle
Platinum Disco - Iguchi Yuka