My first choice is going to be : Kartik from A Great and Terrible Beauty. From the very beginning, we don't know whether Kartik is a good guy or a bad guy. He's been sent to follow Gemma by the brotherhood known as the Rakshana. He follows her all the way to boarding school in England from India. He lives outside the school along with a group of gypsies that he meets. I don't want to give away a lot of the book, but Kartik becomes more and more embroiled with Gemma and her friends. He eventually gets sent back to India for failing his mission. I won't go into any more detail because it really is great to learn more and more about this character as the books go on. He becomes embroiled in Gemma's life and eventually even falls in love with one of the main characters.