Chistopher Walken's performance as Vincenzo Coccotti in that scene with Dennis Hopper was great. "I'm the Anti-Christ. You get me in a vendetta kind of mood, you will tell the angels in heaven that you had never seen pure evil so singularly personified as you did in the face of the man who killed you."
It was second only to the scene between Christian Slater and Gary Oldman (Clarence vs. Drexl) when he went to gather Alabama's personal items.
And of course the scene with Gandolfini(Virgil) and Arquette (Alabama) is also priceless.