Actresses who use a higher-pitched voice for a character
I'm watching Sam & Cat on Nick (and once again, I'm blaming my 5-year-old) and Ariana Grande, the actress who plays Cat, is speaking in a higher-than-normal pitched voice and at first it's a little distracting, then you get used to it, then, it's kind of sexy! (She's 20 now, I'm allowed to say this.) I found an interview online, and that is not her normal speaking voice. Many other actress have done this, Mira Sorvino in "Mighty Aphrodite," springs to mind, and it had the same effect.
The opposite of this would by Missi Pyle who was hilarious speaking in a low register as the stern German flight attendant in the Broadway revival of "Boeing Boeing." Once again, distracting at first, then sexy.