You can't have a list of mobsters without mentioning the man who sticks in the minds of most people: Al Capone. It seemed for years as if law enforcement couldn't touch him. As head of the Chicago-based Italian-American empire known as the Outfit, Capone was guilty of any number of sins, from gambling and prostitution to bootlegging and narcotics trafficking to robbery, bribery and murder. Though his record is long, Capone gained the most notoriety for the infamous St. Valentine's Day Massacre in which seven high-ranking members of a rival gang were shot dead. Though Capone himself had arranged to conveniently be vacationing at the time, there was little doubt the job didn't have the boss's approval. But what finally brought the mobster down was one of his most minor offenses: tax evasion. The lesser crime and lighter sentence it carried meant one of the most notorious crooks of all time served just seven years, six months and 15 days behind bars.