Miku and Luka
Not only do I love Luka but Miku too. Especially with her song World is Mine. And the very song she sings with Luka, World's End Dancehall. If you would like to hear then check out the videos.
Luka was also the third Japanese vocaloid2 made and was released on her birthday, January 30th, 2009.
I would now also like to add in two other vocaloids that I like. The Kagamine Twins, Len and Rin. I am a big fan of there song Butterfly on My(Your) Right Shoulder. I like them when the sing together and separate. Like in Meltdown they both sing versions of the song just not together. I really like both versions. I don't really have a favorite!