I'll admit it, I came late to the Harry Potter phenomenon. I resisted the recommendations from friends to read the early books, considering them the usual tripe marketed at young readers. In the fall of 1999, when no one was around, I picked up Sorcerer's Stone. Less than a week later, I put down Prisoner of Azkaban, and along with everyone else waited anxiously for the next six months for the release of Goblet of Fire. I was surprised by the depth of the characters and the skill of Rowling's prose. Of all the characters, my favorite from the start was the know-it-all little witch from Muggle origins. She was always not just the smartest, but the most level-headed (punching Draco aside), the most responsible, and the most compassionate. I still think she wound up with Ron mostly out of pity.
When the movies rolled around, I thought they nailed the casting on all three of the main children, as well as most of the staff. As time went on, it became apparent that Emma Watson was the most talented of the younger actors, and when it became clear she was going to be much prettier than the books intended, it was too late. She was Hermione, complete with scathing expressions to go with her acerbic wit, growing impatience with her less studious and less thoughtful friends, and a strength that not enough young female characters exhibit in popular fiction. Not an obvious ass-kicking strength, but a moral fiber and toughness that transcends the physical, and an unashamed pride in her abilities that allows her to shrug off the criticisms of her envious inferiors.
There will probably be a few more Harry Potter characters before this list is done, but Hermione tops them all.