One of the ones from the old horse cavalry days: Two privates fresh on the plains from New York are digging a hole to bury a large animal and are arguing what the animal is. One says it is a horse, and the other maintains it's a mule. The camp doctor comes up, and sets them both straight -- "It's an ass, fellas". Later the chaplain walks up, and asks the two privates what they're doing. "We're digging an ass hole."