For me Durotar will always be my favorite zone. It was where I first played wow and I really loved going into the many caves and traveling to echo isles was an interesting quick change of environment. The only thing I disliked was getting that damned goblin warlock’s claw.
For leveling I enjoyed my time in the hinterlands, forest trolls interested me back then and it was really cool to learn more about them during the burning crusade.