I have one absolutely favorite breed and two very close runner ups.
My absolute favorite breed is the Standardbred. The Standard is a complete package, you have a very versatile horse capable of doing Western, English, Gaited, and Driving. They are extremely athletic, very sane, and a very willing/people oriented horse.
My two runner ups are the Thoroughbred, particular to OTTBs due to their heart, athleticism, and huge personalities.
Last but not least is the Tennessee Walking Horse. Love the smooth gaits, their desire to please, and their ability to go all day on a trail.