Well, since my OCs are partly based off myself, I'd think either a Spinosaurus, because they are simply the biggest, nastiest things around. Or a Pteranodon, simply for the flying bit. I've always dreamed of finding some way to fly without a vehicle.
A Stegosaurus is a pretty intriguing life too. Granted, they were known for being pretty dim, but I'd enjoy that, living a very simple life.