These ones I don't know whether they can be considered "rare" enough for the topic, but the gangsters in question are certainly not so well known as they theoretically could be, considering what they did in Akron in the 1910's: this group, headed by Rosario Borgia (considered the n.1 racketeer in Akron at the time), tried to expand their extortion sphere of influence on the big business and prominent people in Akron, Ohio and was so persistent that even the local police refused to be bought off, so Borgia could think of nothing better than putting a bounty on the whole police department, paying a certain sum of money for each murdered policeman (4 policemen were killed before the arrest of the gang and another one after that). Eventually some of them, Borgia including, went to the electric chair (another example contradicting the statement that Lepke Buchalter was the only mob boss to be executed in USA).

Rosario Borgia (the boss)

Frank Mazzano

Pasquale Biondo

Paul Chiavaro

Vincent Damico