I'm sure I'll forget many great actors, so feel free to add your own to this list. I'll also try and find some good quotes for them. Here's one so far:
James Earl Jones in Conan the Barbarian:
"Yes! You know what it is, don't you boy. Shall I tell you? It's the least I can do. Steel isn't strong boy, flesh is stronger! Look around you. There, on the rocks; that beautiful girl. Come to me, my child... [girl leaps to her death] That is strength, boy! That is power! What is steel compared to the hand that wields it? Look at the strength in your body, the desire in your heart, I gave you this! Such a waste. Contemplate this on the tree of woe.[to his guards] Crucify him!"