Ooh, I'll have to think on this one!
Percy Jackson and the Olympians: Percy and Grover
Heroes of Olympus: Leo
Series of Unfortunate Events: Count Olaf
The Outsiders: Johnny
Disney Fairies: I've only read a few, but I'm going to have to go with Rani
Master Cornhill: Tom
Narnia: Lucy, Prince Caspian and Aslan
Hangman's Curse: Ian
The Wingfeather Saga: Peet the Sockman
I'll add more when I think of more books. ^^
~Cat