I recently watched "Predator" on bluray and I think I'm convinced more than ever now that the final confrontation/duel between Arnold and the Predator is the greatest human vs alien duel I've ever seen. What are some other good examples?

Some others that came to my mind,

Ripley vs. queen alien in Aliens
Danny Glover vs Predator
Kirk vs. Gorn
_________________________
I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when my fear is gone I will turn and face fear's path, and only I will remain.