Flying is my favorite. A lot of my favorite Pokemon, like Staraptor and Archeops, are part Flying. They're one of the most balanced types, having 3 weaknesses and resistances, and an immunity. They generally have high Speed, which is useful in just about every battle ever, besides a Trick Room battle. Many also have a decently high Attack stat, or Sp. Attack if that isn't the case. The feeling of being in the air, the thrill of flying... it's exhilarating!