ABE "KID TWIST" RELES- Abe Reles was a natural born killer. He was a violent and unpredictable man and an early member of the charmingly named Murder, Inc. This was a notorious "enforcement arm" of the American and Jewish Mafia believed to have killed up to 1,000 people during the 1930s and 40s. Reles was renowned for using an ice pick on his victims, which he would ram into their brains through their ears. Even day-to-day he was unstable and would sometimes attack innocent bystanders; he once murdered a parking lot employee for not bringing his vehicle up fast enough. This notorious hitman was arrested in 1940, but despite being implicated in "dozens" of killings, he was able to wriggle out of the death penalty by ratting on his boss Louis Buchalter and other key members of Murder, Inc. Informing didn't work out well for Reles, though, he was found dead on the pavement outside his hotel room on November 12, 1941. The press called him "the canary who could sing, but couldn't fly."

SALVATORE "SAMMY BULL" GRAVANO- "Sammy Bull" Gravano was another Mob rat who evaded justice by squealing on his colleagues. Born in Brooklyn, New York in 1945, Gravano worked his way up from small-time theft and street fighting to become the protégé of crime boss Joe Colombo in the late 1960s. Under his mentor's guidance, this cold-blooded criminal committed a number of murders, which won him respect and approval. Eventually, issues arose with another Colombo mobster and Gravano was allowed to leave the family to avoid any conflict. Continuing his Underworld existence, Gravano joined the Gambino crime family. And as well as making this career move, he also achieved significant influence – and became a multi-millionaire – through construction and trucking business interests. Gravano achieved underboss status working for the head of the Gambino family, John "the Teflon Don" Gotti. Then, after being arrested along with Gotti in December 1990, Gravano turned stool pigeon and sold his boss down the river. Despite Gravano's involvement with at least 19 killings, in 1994 the state sentenced him to only five years in prison. And because he'd already served four of them, his sentence amounted to just one year's jail time.

SAM "MAD SAM" DESTEFANO- Sam DeStefano worked for Chicago crime syndicate the Chicago Outfit and was one of their most feared and brutal enforcers. Beginning his career as a political fixer and petty criminal, DeStefano became a member of Chicago's Forty-Two Gang in 1930. And later, in the 1950s, he became one of the city’s first loan sharks. This gangster would often lend money to vulnerable clients, like drug addicts. When they failed to pay up on time, he would bring them to his soundproofed chamber in the basement of his house and sadistically torture them until they died. He would often kill clients who owed him money simply in order to scare the rest into paying. And according to other criminals, he foamed at the mouth while he was torturing his victims. DeStefano's downfall came in 1973, when he and two associates were arrested for a murder committed 10 years earlier. Worried about the media circus surrounding him and the possibility that DeStefano might turn informer, his associates ambushed and shot him before he could be brought to justice.

FRANK "THE DASHER" ABBANDANDO- Frank Abbandando was a ruthless New York career hitman believed to have been responsible for as many as 30 murders. Abbandando killed most of his victims by stabbing them in the chest with an ice pick, although he was sometimes partial to a meat cleaver as well. Rounding off his nice-guy portfolio, "The Dasher" was also an alleged sexual predator and rapist. Like Abe "Kid Twist" Reles, Abbandando was an early core member of the Murder, Inc. hit squad and took part in one of the gang's most notorious crimes: the murder of the Shapiro brothers – one of whom was buried alive. Abbandando was arrested in May 1940. Throughout the trial he was confident that his associates would fix the case in his favor. At one point, he even whispered a threat into the presiding judge's ear. But to Abbandando's surprise, aided by the testimony of associate-turned-stool-pigeon Abe Reles, he was sentenced to death by electric chair and executed in February 1942.

HARRY "PITTSBURGH PHIL" STRAUSS- Harry "Pittsburgh Phil" Strauss was another Murder, Inc. stalwart and, allegedly, the organization's most violent member – which is saying something. Strauss is thought to have dispatched with at least 30 people during his dark career. In fact, according to some historians, the figure is somewhere between 50 and 100 – possibly more, if other sources are to be believed. A well-organized and remorseless murderer, "Pittsburgh Phil" often carried a gun and an ice pick in his suitcase, along with a change of clothes and a length of rope. And when carrying out hits, he would sometimes torture his victims by wrapping a rope around their head and neck, so that any movement would cut off their oxygen supply. Interestingly, despite his nickname, this hitman was a Brooklyn native who had never even visited Pittsburgh. Strauss was arrested 18 times but was never convicted, until the downfall of Murder, Inc. in 1940. During his trial, his attempted insanity plea failed, and he was executed on June 12, 1941 by electrocution.

THOMAS "TOMMY KARATE" PITERA- Thomas Pitera was a hitman for the Bonanno crime family in the 1980s. He was bullied as a child, which may account, at least in part, for his obsession with martial arts and his violent, sadistic behavior. Well known for his fighting skills, Pitera was given the nickname "Tommy Karate." Astoundingly, Pitera is believed to have carried out as many as 60 murders during his career with the Mob. Taking pleasure in his work, he often dismembered his victims after killing them and would cautiously bury them in plastic or in suitcases, always careful to inter them deep enough to prevent police dogs from finding them. With his crew, Pitera frequently robbed and murdered drug dealers and resold their products. He also liked to keep trophies like jewelry, which is a classic trademark of deranged serial killers and not in keeping with Mafia "etiquette." Pitera was indicted in 1990 for leading a drug-dealing operation and for his involvement in several murders. The hitman’s attempts to get a reduced sentence have so far been in vain, and currently he is still serving a life sentence at the Federal Correction Complex in Allenwood, Pennsylvania.

JOSEPH "THE ANIMAL" BARBOZA- Joseph Barboza was born in New Bedford, Massachusetts in 1932. Born to Portuguese immigrants, he was also a skilled chef and was well known for his authentic Portuguese cuisine. He even graduated as a chef and mastered French cooking. But by his mid-twenties, Barboza was heavily involved with the New England Mafia, performing contract killings for the Patriarca crime family. Barboza earned his nickname "The Animal" in an altercation that sounds like a scene out of Goodfellas. While drinking one night, he was told off by an elderly man who didn't appreciate his crude behavior. In retaliation, Barboza slapped the old man in the face. Underboss Harry Tameleo shouted at Barboza, saying, "I don't want you to ever slap that man. I don't want you to touch anybody with your hands again." So Barboza bit the man's ear – and, according to some sources, chewed on his cheek as well. Barboza was arrested in 1966, but as with many hitmen before, and after him, "The Animal's" information was more valuable than his skin. Negotiating his way out of trouble, Barboza was able to escape with a one-year prison sentence by ratting on other members of his organization. In the end, on February 11, 1976, Barboza was murdered, despite being one of the first criminals to use the witness protection program. He was killed by four shotgun blasts at close range before he even had a chance to draw his gun. Maybe he should have stuck to cooking.

ROY DEMEO- Roy DeMeo was the leader of the infamous DeMeo crew, a gang of contract killers who killed for the Gambino crime family. Between 1973 and 1983, he and his associates murdered between 75 and 200 people, mainly using the "Gemini method," which DeMeo developed to decrease the messiness of disposing of a body. The DeMeo crew would generally lure their victims to the Gemini Lounge, where one member, allegedly almost always DeMeo himself would shoot the victim in the head with a silenced pistol and immediately wrap the wound with a towel to stem the blood flow. After that, another gang member would stab the victim through the heart to reduce the blood flow from the head wound. The body was then hung upside down in the bathroom to drain and was later dismembered on plastic tarpaulins and sent to the Fountain Avenue Dump in Brooklyn. This method was so successful that most of the crew's victims were never found. However, in 1982, the FBI became suspicious about the number of people who had disappeared at the Gemini Lounge and launched an investigation. Several of DeMeo's associates were arrested, and the hitman spent his last few days in a state of constant panic, convinced that he himself would be assassinated – and he was right, his body was found in the trunk of a car in late January 1983. He was most likely killed by members of his own organization.

GIOVANNI "THE PIG" BRUSCA- Giovanni Brusca is a former Sicilian Mafia member who once claimed to have murdered as many as 200 people. Born in Sicily in 1957, Brusca began working as a driver for the head of the Corleonesi faction of the Mafia when he was 20 years old. He was nicknamed "The Pig" for his unkempt appearance. One of Brusca's most gruesome acts was kidnapping the 11-year-old son of a gang-member-turned-informant and torturing the boy for more than two years in an effort to get the fellow mobster to retract his testimony. The boy was later murdered and his remains were disposed of in sulfuric acid. Brusca's 1992 murder of anti-Mafia crusader and magistrate Giovanni Falcone, along with Falcone's wife and several bodyguards, eventually led to "The Pig's" arrest in May 1996. The Mafia killer managed to secure improved treatment by acting as an informer himself, which caused controversy in Italy, with many of his victims' relatives reacting with outrage over the government's cooperation with criminals. Damningly, Brusca's confessions alleged that ex-prime minister Silvio Berlusconi paid the Mafia to have things "kept in order."

RICHARD "THE ICEMAN" KUKLINSKI- Richard "The Iceman" Kuklinski is one of the most prolific contract killers ever to have worked for the Mafia. Having taken his first life when was just 13, he claimed to have personally committed as many as 250 murders. The hulking Kuklinski was born into an abusive household in Jersey City, New Jersey in April 1935. He was violently beaten by his father, who allegedly beat Kuklinski’s brother Florian to death. Kuklinski's older brother Joseph was also convicted of raping and murdering a 12-year-old girl. And Kuklinski himself was beaten by his mother as well and fantasized about killing his father. As a kid, Kuklinski sadistically tortured and killed neighborhood animals for fun and took out his anger fighting and killing local bullies as well. Working as a hitman for Mafia crime families in the 1950s, he would stalk bums and kill people who had offended him to practice his skills and master his craft. Kuklinski earned the nickname “The Iceman” because he would sometimes freeze the bodies of his victims in order to mislead the police as to their time of death. This most cold-blooded of killers was eventually arrested in 1986, based on the testimony of undercover agent Dominick Polifrone. He was sentenced to several consecutive life sentences and died in prison in 2006 before he could give evidence against crime boss Sammy Gravano.