Jonathan Anthony Wisniski (born September 20, 1951) is an American professional wrestler, better known as Greg "The Hammer" Valentine. He is the son of wrestler Johnny Valentine. In the course of his career, which has spanned over four decades, Valentine has held more than 40 championships, including the NWA United States Heavyweight Championship and the WWF Intercontinental Championship. An alumnus of the World Wrestling Federation and World Championship Wrestling, he was inducted to the WWE Hall of Fame in 2004.
- Alabama Wrestling Federation Heavyweight Championship
- Alabama Wrestling Federation Tag Team Championship
- American Wrestling Association Midwest Tag Team Championship
- American Wrestling Federation Tag Team Championship
- Bad Boys of Wrestling Heavyweight Championship
- Canadian Grand-Prix Wrestling Heavyweight Championship
- International World Class Championship Wrestling Heavyweight Championship
- International Wrestling Association Heavyweight Championship
- NWA Canadian Heavyweight Championship (Toronto version)
- NWA Mid-Atlantic Heavyweight Championship
- NWA Mid-Atlantic Tag Team Championship
- NWA Mid-Atlantic Television Championship
- NWA Television Championship
- NWA United States Heavyweight Championship
- NWA World Tag Team Championship (Mid-Atlantic version)
- WCW United States Tag Team Championship
- NWA North American Heavyweight Championship
- NWA Americas Heavyweight Championship
- NWA Beat the Champ Television Championship
- North State Wrestling Alliance Tag Team Championship
- NWA North American Heavyweight Championship
- NWA United States Tag Team Championship (Tri-State version)
- NWA Western States Tag Team Championship (1 time)
- National Wrestling Federation World Tag Team Championship
- Prime Wrestling Tag Team Championship
- Portland Wrestling Pacific Northwest Heavyweight Championship
- Professional Wrestling Federation Heavyweight Championship
- Pro Wrestling Ohio Tag Team Championship
- Pro Wrestling Revolution Heavyweight Championship
- Windy City Pro Wrestling League Heavyweight Championship
- World Wrestling Council Caribbean Heavyweight Championship
- World Wrestling Council Universal Heavyweight Championship
- WWE Intercontinental Championship
- WWE World Tag Team Championship
