The basic structure of a story is a time tested formula. Protagonist versus antagonist -- whether that antagonist be another person, a creature, or even the elements.
Just like parents, writers aren't really supposed to favor any one character over another. But it happens. Some of them are just plain fun to write.
For anyone keeping score at home, this is a combination of two writing prompts, since they complement each other. In my case, they also happen to be so inter-related that I didn't feel right separating them.
My favorite protagonist comes from a NaNo project a few years back. His name is James Garreth. He's actually younger than most of my main characters usually are ... he's 18 and on the run from a pair of FBI agents.
One of whom isn't really an FBI agent, but a medical doctor specialized in the condition afflicting Garreth. Doctor McEwon also happens to be my favorite antagonist. Mostly because he's just plain creepy. And unethical. He has a bit of a sadistic streak as well, but that sort of goes hand in hand with the creepy unethicalness that oozes from him.
Where Jason Garreth is fun to write due to his youthful, nothing-can-stop-me perspective, McEwon has a jaded cynical outlook on life that makes them a mirror pairing. In the scenes that they share page space, they have an interesting interplay that helps (in my opinion, at least) capture the theme of that particular project.
I'm not usually big on theme, but in this case it surfaced in the story and made it a more compelling read. Not that many other people have read that book. It suffers the fate of many NaNo projects, sitting dejectedly on my computer waiting for me to have some free time to go through and really give it a good rewrite.