In terms of legitimate tough guys, MMA legend Ken Shamrock is up there with the very best on this list. In fact, when it comes to credentials, there's only really Brock Lesnar who can rival Shamrock. The difference between the two, though, is that Shamrock's nickname was far cooler than Brock's and this was only amped up further with Ken's trademark intensity and loose cannon persona. Shamrock was dubbed The World's Most Dangerous Man during an ABC News feature way before he stepped into a WWF ring. But once a part of Vince's organisation, the former UFC Superfight Champion did all he could to live up to this nickname. What made Shamrock unique was that the audience actually believed he was likely to flip out at any minute and possibly turn any worked wrestling match into a straight-up shoot contest. There had been other competitors with an MMA background who had turned to pro wrestling, but Shamrock was the first one to be positioned as a superstar and to truly have his credentials put out there for fans to be aware of. Many believed that Shamrock was destined to become WWF Champion - there are even stories out there that he was indeed supposed to be at one point - but for whatever reason his WWF run came to an end in 1999 and a return to MMA would follow before a few fleeting wrestling appearances since then, including being recognised as TNA's first ever World Champion.
