Let's see.
My favorite by far has to be Shinku.
Especially her Kunkun and embarrassment reactions are heart-melting
Hinaichigo and Kanaria are on the same level, they're cuteness factor to the max. Although what really sold me to Kana was her battle with Suishou.
And Tomoe, well, I like her
I'd have added Suigintou and maybe Sui but I thought I have to draw the line somewhere