Lists are always popular blog reading, for some reason — so here is the latest I could find, from Gothamist:
Organized crime has always thrived on intimidation and brutal acts, but sometimes the violence is unspeakably gruesome. Here are some of the most notorious mob hits, from a gruesome payback to the stool pigeon who couldn’t fly:

Al Capone had an alibi for the massacre
THE ST. VALENTINE’S DAY MASSACRE: Considered the “most infamous of all gangland slayings in America,” seven men were lined up against a Chicago garage’s wall on February 14, 1929 and executed by machine gun-wielding men who posed as police officers.
The victims, whose bodies were ripped apart by the gunfire, were members of Bugs Moran’s North Side Gang, who had been encroaching on Al Capone’s territory. Months earlier, Moran also orchestrated a drive-by shooting, attacking Capone at a diner, giving Moran the dubious distinction of innovating the “drive-by” for the modern era.
Moran wasn’t killed because he happened to sleep in that day. Capone wasn’t charged with the murders because he had an alibi (the ol’ “I was in Florida” excuse) but government officials redoubled their emphasis on stopping Capone. In 1931, Capone was put away for tax evasion.
The Golden Dragon Restaurant Massacre: In 1977, two factions of the Triads, the Joe Boys and the Ping Boys, were battling over money from illegal firecracker sales in San Francisco. The Ping Boys got 10% on the sales, and the Joe Boys wanted to steal that, but the Ping Boys managed to thwart them, killing one Joe Boy member and injuring others. But two months later on September 4, 1977, the Joe Boys went to exact their revenge, by heading to the Golden Dragon Restaurant, where Ping Boy member Michael Louie was dining.

Three masked men entered, firing all around. Five people, including two tourists, were killed and 11 others were wounded. None were gang members and the event prompted the San Francisco Police Department to form an Asian Gang Task Force.

John Gotti was worried Castellano would kill him first
SIDEWALK KILLING OF PAUL CASTELLANO: Just blocks from Grand Central Terminal and the United Nations, Sparks Steak House is located in the heart of New York City’s busy Midtown Manhattan business district. And on December 16, 1985, with the city full of holiday visitors, the location was chosen as the spot where four men gunned down Gambino crime boss Paul Castellano and underboss Thomas Bilotti.
John Gotti, another Gambino underboss, was the mastermind of the hit, because he wasn’t pleased with how Castellano was running the crime family. Gotti was also concerned that he would eventually be killed so he acted first. After reaching within the Gambino organization and to other crime families for support, a plot was devised to have Castelleno pay his respects to the son of a deceased gangster at Sparks.
As the pair were stepping out of a car to head into the restaurant, the men, wearing long light colored trench coats and black fur Russian-style hats, fired repeatedly at them. Castellano was shot six times in the head, his body on the sidewalk. It turns out that Gotti, who eventually seized control of the Gambino crime family, had been across the street in a car watching the hit—he drove past the restaurant to see that Castellano was dead for good.
MURDER OF BUGSY SIEGEL: Born to an immigrant Jewish family in Williamsburg, Brooklyn, Benjamin “Bugsy” Siegel ran a bootlegging operation with Meyer Lansky in his youth. Then he and Lansky worked with the Genovese crime family, with Siegel helping kill Lucky Luciano’s rivals so Luciano could rise to the top. He moved West, starting a numbers racket and extorting money from Hollywood figures as well as spurring on development in Las Vegas.
Still, he was a “textbook sociopath,” who had little remorse. Lansky once said, “He was even quicker to take action than those hot-blooded Sicilians, the first to start punching and shooting. Nobody reacted faster than Benny.” And his nickname was derived from his “tendency to ‘go bugs’ whenever he was angered or thwarted.”
On June 20, 1947, Siegel was reading the Los Angeles Times in the Beverly HIlls home of his girlfriend Virginia Hill when someone fired through the window with a .30-calliber M1 carbine, hitting him 3-4 times in the head, with one shot reportedly blowing an eye out of his head. The murder was never solved.
Read complete article at Gothamist