My vote has got to go with Jimmy Conway. I was always impressed with how De Niro played the character from his late twenties to his mid fifties, always looking totally natural in that role.

I only wish the character of Jimmy Conway
could have been developed a little more.

A difficulty with this question is seperating the characters as they came across in the movie and what else we know about them. I was tempted to go with Henry. Though he is a rat, I had some respect for him. Ray Liotta's great performance made me sympathetic to the guy and the way he turned his back on what was he part of and appeared to begin a new life.

However as I find out more about the real Henry Hill's shameless self publicity and his resumption of drugs and crime, it's difficult to see him as anything other than a traitor.

Jimmy Conway is the best in my book!