my お気に入り is SAF2 MIKI. i like her 星, つ星 pattern, and her color scheme is cool too. I also think the designers did a good job on emphasizing the fact she is a robot によって adding the visible joints at the limbs.
The cutest vocaloid for me is vocaloid oliver because he looks and sounds unique. Some people 発言しました he sounds and looks like Len but HE IS NOT!! He is もっと見る than that. I like his monster type appearance and he looks innocent though
I have a lot of ボーカロイド I think are really cute! ^.^
Hatsune Miku, of course, is the classic example of an adorable Vocaloid; cute character デザイン (I especially 愛 her V4 and Chinese designs), lots of lush hair, smallish, skinny build, and sweet voice. Also, her Japanese accent in English and Chinese is just too cute!
Kagamine Rin was pretty much MADE to be cute, with her childlike vocals, short and skinny design, and her short but sweet blonde hair tied up with a big white bow! Like Miku, she has a really cute accent in English!
Kagamine Len may be fangirled over excessively, but I, too, think he's really cute. The fact that he's voiced によって a girl due to his adolescence, the fact that he wears a freakin' PONYTAIL, and the shy/"tsundere" aura he gives out all lend to his boyish charm. Ditto with Rin for the accent.
Megurine Luka may be a 20-year-old who's supposed to be "sexy," but something about her is just sweet and charming. Maybe it's her long (or...medium length for an アニメ character XD) ピンク hair, または her big, beautiful blue eyes, her sweet, soft voice または her Japanese accent in English. または just some of her songs, like "Toeto" または "Dreamin' Chuchu."
I honestly 愛 both the designs and voices of the two Korean Vocaloids, SeeU and Uni. My opinion that Korean is a nice-sounding language helps this. They both have really cute designs (SeeU is a catgirl and Uni is practically a walking strawberry), cute voices (especially Uni), and it's cute when they try to sing in other languages as well.
I like pretty much all the Chinese Vocaloids, but to me, Luo Tianyi is によって far the cutest. Her adorable, innocent-looking design, sweet, introverted personality, and sweet, girly voice all lend to this. (Also, I just find Chinese a cute language for some reason.)
As for English Vocaloids, Avanna and Oliver take the cake. Oliver is a child voiced によって a child, with a cute British accent and a nice design, but because of his "monster" design, he is often used for horror songs. Aside from that, he is very cute, and so is his voice 芝居 counterpart, Puppycat. There's just something operatic about his voice. And Avanna is also very cute, with her anime-like design, her elf-based character, and her sweet, soft, humanlike voice with her Irish accent, which is ironically often used to portray a robot, possibly because she is most 人気 in the West, where Vocaloid isn't as common, but this adds to the charm.
Kaai Yuki is, like, one of the ultimate cutest ボーカロイド ever, almost によって a FACT, as she is a natural-looking (brown hair, brown eyes), natural-sounding Vocaloid, voiced によって a young child with a super-sweet voice and surprisingly good English. Like, how can Yuki NOT be cute?