The first Terminator, definatly. It's so full of win. You have "I'll be back", the gunshop scene, the eye operation scene and much much more.
By the way, a brilliant detail in the eye operation scene: after putting his glasses on, he checks if his hair looks alright. That cracked me up when I payed attention to it. A killer robot from the future who feels the need to have a proper haircut, brilliant.
Honerable mentions go to: Predator for "Get to da choppaaa!!" Running Man for the incredibad but downright hilarious oneliners, Total Recall for overal win and Conan for utter cult status.