Arnold Schwarzenegger as the Terminator deserves a certain amount of credit -- when he shows up, he shows up. He drops into frame, having travelled from a post-apocalyptic future ravaged by a war between robots and humans, and is immediately terrifying. His immense stature, extreme physical fitness, and total lack of clothes make it clear to the audience that although he has a human form, he is definitely not a person. The fact that at this point in time Arnold was a very inexperienced film actor actually works to his advantage: his stiff walk and straightforward line delivery add to the overall feeling that the Terminator is something trying very hard to look and act human, but isn't quite there yet.