Joe Valachi......although if my memory serves me correctly he was not the first person to talk he was the first high-profile mafioso to talk. I say him because of what the Mafia is today, if the Mafia was powerful and still growing as it did in the 30's/40's/50's my vote would go to Lansky/Luciano, but what they did was not influential enough for what is going on today. Valachi had more of a lasting influence on the mafia, positive or negative (depending on how you look at it) it was still the most influential in terms of how they act today.