Lucky Star

With added bonus: Loituma, Final Fantasy Style!

(The characters here are Meiko (in red), Kaito (in blue) and Hatsune Miku (in green). The first two are from Vocaloid 1, Miku is from Vocaloid 2)
One little detail about this song... You do NOT want to hear any of the characters attempt to sing it. Honestly. And if you do, try this video:

As you can hear, Vocaloid voices can not speak, they can only sing~!

Soukyuu no Fafner OP (Vocaloid Rin & Len)