I feel a tad silly admitting this one (her being a robot and all) but, Arcee from the 80's Transformers series and movie. She's just such a sweetheart and I just want to give her a big hug.
I love her G1 design because it reminds me of the retro design of humanoid robots. I also love her new design in the Animated series, I can't wait for a figure of this one.