Bullingballs is the Master of Hardness. He was the lone Tauren who stood apart from his tribe during the War of the Ancients, when they became part of the Burning Legion. His tribe became what we now know as the Doomguard. More of the story of how Bullingballs gained his unnatural power can be found under the name Hardness.
Bullingballs has been accused of being a trade troll, but anyone who actually knows him knows that this is clearly not the case. For he is a Bull meant to inspire people, not annoy them. Giving rise to the term Bulling.
He is also the star of a Youtube video series called "The Hard Adventures of Bullingballs."