Pull-ups are my favorite exercises for the mid/upper back.
Done with a wide grip, pull-ups will give you a flare in your lats, that makes your upper body appear wider.
Training the mid/upper back with pull-ups plays an important role in helping to get rid of man boobs. This is because your back houses the second largest muscle group after your legs. So when you train your back, you benefit from bigger testosterone boosts than you do when you train other, smaller bodies of muscle, like in your chest, shoulders, abs and arms.