I voted for Rika. I don't think I need to explain why.
Then, despite the fact that she's the villain in Kai, I voted for Takano because I pretty much felt sorry for her at the end of the series. I know she would have been a very nice person if only her parents hadn't died
(Perhaps she would have looked like a grown up Lambdadelta 
).
And my last vote goes to Gin-sama (Other), because her making fun of Takano was just epic win.