Animes with characters that have split personalities

Moka Akashiya ~

The one you see to the right is the Pink Haired, Adorable, Ditsy little cutie. Then on the Left is her self as a vampire. When the Rosario around her neck comes off then she transforms into a vampire. Her vampire side has a completely different personality than Pink Haired Moka. She practically has two souls in one body. :)

Basically, a lot of people in Rosario + Vampire have split personalities ~

BLEACH - Ichigo Kurosaki & his hollowfied-self

Akito and Agito Wanijima
when the eyepactch covers the left eye he becomes Agito (he is evil) and when it covers the right eye he become Akito (he is nice)

Moon Phase

Since you already mentioned Yu-Gi-Oh...

(insert Challenge Accepted here)

Rosario+Vampire has Moka.

Inuyasha!!!! :D

Hatsuharu-kun from Fruits Basket there's a time where'll he'll act all nice and there's a time where he won't be so nice and literally wreck havoc.

Johan Liebert from MONSTER

He said that's there a monster inside him and that what makes him kill others and he get other to kill them self. Johan is so curl when hes this.He even killed his own foster parents

But other times he different hes as sweet as can be, he helps kids and others people.A few times he even saved them from dying.

He believes that's there a monster inside him. he tell his twin sister Anna to kill him because the monster inside him is getting bigger and he can't control it any longer.That's right after he killed there faster parents.

if that's not split personalities then i don't know what is. X)

Bleach has Ichigo/Hichigo
Kara no Kyoukai has Shiki
Mirai Nikki has Yuno

i would say Stein has a split personality

Shiro/Red Man from Deadman Wonderland.

Shiro is a bubbly girl and has lots of energy, but when she's the Red Man her whole other personality changes.

Amu-chan from shugo chara

Zetsu-san! ^^ The white side is whimsical, the black side is serious. Here's a pic of him literally splitting in half:

Natsuki, when his glasses come off he becomes a totally different person

Launch from Dragon Ball. her original hair colour is purple. She's kind as in purple hair. When she sneezes her hair turn blonde and became the opposite...

Nura Rikuo from Nurarihyon no Mago

yukiko~ when she takes of her glasses, she's a completly different person~ it's like natsuki from uta no prince sama XD

Cavendish (One Piece)

His next personality is Hakuba it awakens when he fall asleep.........a monster who loves to kill...........eh he he

yogi from karneval
(and tiky mikk from :d.gray man)

Yu-Gi-Oh (Yugi), Dragon Ball Z (Launch)

I'd say Touko Fukawa from danganronpa. When she passes out her murderous side comes out.