Gene Tunney
Gene Tunney broke the mold of heavyweight fighters in his era by being more of a tactical boxer than an all-out slugger. He would use his left jab to box and break down his opponents rather than fighting the traditional highly aggressive heavyweight style.
He was the world heavyweight champion and is known for twice defeating the great Jack Dempsey. The only loss of his professional career came against middleweight legend Harry Greb. Tunney was never defeated as a heavyweight and that is quite a fete.