There's an art to caving in a human face or blasting someone in the package like those mixed martial arts fighters do. And thanks to the Lion's Den in Scottsdale, anyone can learn no-holds-barred sparring. UFC Hall of Fame inductee and "the world's most dangerous man" Ken Shamrock heads the dojo, where controlled muay thai sparring techniques are taught to men and women of all skill levels. World-class instructors also teach wrestling, boxing, and basically any other kickass skill out there.