For Vocaloids, check the wiki page.

Hmm i will try

Hatsune Miku, Kagamine Rin, Kagamine Len, Megurine Luka, KAITO, MEIKO, Camui Gakupo, Megpoid Gumi, Kaai Yuki, Hiyama Kiyoteru, Sweet ANN, Lola, Leon, MIRIAM, prima, tonio, miki, big al, lily, vy1, vy2, gachapoid, iroha, piko, seeu, rion, oliver, fukase, vflower, cul, yukari, bruno, clara, maika, ia, lapis, merli, tianyi, galaco, mayu, avanna, dex, daina, yanhe, yohio, nana, petit, kokone, anon, kanon, zunko, rana, chika ,xin hua, ling, cyber diva, cyber songman, arsloid, ruby, unitychan, stardust, una, uni, nemu, longya, azuki, matcha, lumi, akari, komachi, moke, qingxian, sora, hime, mikito, fuiro, po-uta, teto, zundamon, neru, haku, defoko, ruko, momo, sonika, sachiko, mikuo, Haruka Nana, Otone Peke, Zatsune Miku, Sukone Tei, Kazehiki

I don't think anyone can give you a complete list of UTAUs there are too much-

With utau, anyone can make their own in a week short, so i’d just stick with the popular ones.

Aight, here’s mine.

Kasane Teto, Defoko, Momo Momone, Yukone Ruko, Namine Ritsu, Kikyuune Aiko (here comes the rest of em) Kikyuune Akio, Kikyuune Akiko, Kikyuune Akihiko, Fuu, Harouka Aki, the rest of the Studio VOXYZ gang, Aiko Ishiame/Feirune

Fukase, Len, Rin, Miku, Kasane Teto, Ruko Yokune, Oliver, Kaai Yuki, Fukase, Arsloid, dex, daina, piko, VFlower, Megumi (utau), Momo Momone, Gumi/Megpoid, Gachapoid, Macne Nana, Macne Coco Black, Macne Coco White, Luka, Meiko, Kaito, Otomachi Una, Uta Utane/Defoko, IA, Maika, YOHIOLoid, Cyber Diva, Cyber Songman, Gakpoid, MAYU...

Thats all I can think of right now

EDIT: heres some synthv too

Tsurumaki Maki, ANRI, Genbu, SOLARIA, ASTERIAN, kevin, Yi Xi, AiKO, Mei (I think her name is Mei), Eleanor Forte

Hatsune Miku

Kaito

Kagamine Rin

Gumi

Kojiloid

Aoki Lapis

Flower

Macne Nana

Masaoka Azuki

Avanna

Cul

Cyber Songman

Kaai Yuki

Kagamine Len

Kizuna Akari

Luo Tianyi

Mayu

Merlí

Anon, anon

Chika

Meiko

Anri Rune

Vy2

Cyber Diva

I found that list in Google somewhere, idk if there all vocaloids or not