I think pretty much the whole [i]moe[/i] concept from anime fits into this - cute little girls who are meant to evoke protective, fuzzy feelings in guys. Some of these would include:

Rei Ayanami - Neon Genesis Evangelion
Sakura Kinomoto - Card Captor Sakura/Tsubasa
The entire casts of Lucky Star, Strawberry Marshmallow, Poptan, etc.

In Western shows I can only think of a couple:

Sierra - Dollhouse
Kaylee and River - Firefly

Maybe I've just been watching too much Joss Whedon?