Hanibal Lector, he is in the movie for like a total of 13mins and somehow he is just the badest dude in cinema history. Pure Brilliance.
I am a bit lazy just now to look at my dvd's or think too hard, but off the top of my head:
Cyrus The Virus - Con Air
Dennis Hopper's character - Waterworld
King Edward (Longshanks) - Braveheart
Agent Smith - Matrix (just the first matrix)
and my last one I would like to mention, Kiefer Sutherland as the guy n the other end of the phone in "Phonebooth".