Draft horses - Clydesdales in particular, but also plain old mixed-breed big guys.

Uncle Lonnie had a team of big of huge blue-grey draft horses that were used around the farm, and to pull kids on "hayrides" around Halloween - they were mostly Percheron, but about a foot or so too short to be purebreds, and had backs so broad you could have set a picnic on 'em ... but they were sweet as could be, adamant about always being on the proper side (woe be to the new guy who tried to yoke them together wrong) and basically like big old puppies when not in yoke. Once in their yoke, though, they were all business, unless an apple or sugar cube appeared - then you'd have better had two of whatever it was!