My hobby is collecting things. Here's a list of ~40% of named Vocaloids.
Maika / Meiko / miki / Miku
Len / Leon / Ling / Rana / Rin / Ring / Rion / (Anri) Rune
(Sweet) Ann / anon / Avanna / Nana
Yuu / Yuki / Yukari
Mayu / Mew (Miu)
Lola / Lorra
Kyo / Kiyoteru
For the next male Vocaloid, I suggest the name Joe.