My list
in no particular order:
(couldn't narrow it down to 10)

Al Pacino
Robert De Niro
Joe Pesci
Michael Imperioli
Ray Liotta
James Gandolfini
Vincent Pastore
Frank Vincent
Michael Madsen
Edward Norton
Brad Pitt
James Caan
Harvey Keitel
Johnny Depp
Steve Buscemi
Dominick Chianese
Andy Garcia
Paul Sorvino
Chuck Zito
Antonio Banderas
Benicio Del Toro
Kevin Spacey
Sean Penn
Bruno Kirby
Joe Mantegna