The Biker gimmick hands down. The Undetaker was humanized and given freedoms he never had before allowing him to become a better performer in the process. Ministry Undertaker was cool too. The Undertaker in the beginning of his run as the dead man in the 90's was one of those once in a lifetime effective gimmicks that became larger than life because of how everything looked, sounded, and felt but when you really think of it he was just one of many gimmicks in a cartoon company catered to children. His gimmick was to scare children or something. They had a big fat Samoan guy playing a Japanese Sumo wrestler that sat on people, a Clown who was evil at one point, Lex Luger a muscle bound freak, right down the line to the plain absurd gimmicks like Mantaur, Phantasio, and Waylon Mercy. The Undertaker was the best of them all but he was just another cartoon freak of many. It took becoming the Biker guy to really bring the best out of what Mark Callis was capable of.