Kobato OP - Magic Number

The opening theme of the currently airing anime, Kobato, Magic Number is by Sakamoto Maaya. The cover is a collaboration of nico artists. Great song, great cover! Muutan's pretty good at covering Maaya's songs.
Vocal, chorus, animation: Muutan (むうたん) user/1873791
Electric/Acoustic Guitar: Papillon Makoto (パピヨン誠) mylist/1066071
Keyboard, movie: Gossun (ごっすん)(otherwise known as gothlolihime (ゴスロリ姫)) mylist/7038088
Bass, mix: Pachi (ぱち) mylist/7273462
Drums: Guu (ぐー) mylist/7112928

(Late) Halloween Edition

Nice Halloween themed cover by Usa.

Usa's (うさ) mylist/4168640



Another Halloween themed cover by Topi and Milia

Milia's mylist/3388871
Topi's (とぴ) mylist/7349500

On a related note, nicovideo now allows embedding of videos for most formats (previously restricted to certain blogs) as you can see. Oh, it comes with ads, no wonder.