Revealing mistake: After Reese blasts the Terminator with his shotgun while at the Tech-Noir nightclub there should be huge holes in the Terminator's shirt and jacket, but there are none.
Continuity mistake: When Reese and Sarah are fleeing from the Tech-Noir nightclub, right when the Terminator jumps on the car they're driving away in his hairstyle magically changes.
Audio problem: When the Terminator breaks into the police station, he has an auto-shotgun in his left hand, and a machine gun in his right. Before he kills the power in the building, he comes to the end of a hall, points his shotgun through a doorway, and shoots. A machine gun sound is used for the blast, instead of a shotgun sound. (01:00:28)
Continuity mistake: When the Terminator says "I'll be back" he walks out of the police station. The cop inside the building looks out of the window, looks very surprised, and you can see the headlights from the car shining on the cop's face. When we see the car just before it comes crashing through the building the headlights aren't on. In the next shot of the cop the headlights are still shining on him. (00:57:25)
Continuity mistake: In the Tech Noir Bar, the same woman - blonde with a pink or orange dress - must have come dancing with her twin, because while she's sitting behind Sarah Connor when the laser beam is pointed at her, she's also dancing near Arnie. The T-800 moves past her when he sees Sarah Connor and moves to shoot her. (00:35:05)
Continuity mistake: When The Terminator's stolen police car is shown up close in the parking structure, the motto on the left side of it reads "to care and to protect." After the car crashes, you can see the motto on the left side again, but this time it reads "Dedicated to serve." The car's trim and position/orientation/color of the police emblem change as well. (00:45:50 - 00:50:20)
Audio problem: Towards the end of the movie, after the tanker is blown up with the terminator inside, Sarah and Kyle are relieved that he is finally 'dead'. When the terminator gets up from the huge fire in his metal form, Sarah screams twice, however when she screams the second time, her mouth doesn't actually move. (01:30:10)
Continuity mistake: When the Terminator enters the police department and he bends over to say "I'll be back" you can see through his shades and he has both of his eyes, despite cutting one out in an earlier scene. (00:59:35)
Visible crew/equipment: When the Terminator is blown up inside the gas truck and you think it is destroyed, Linda Hamilton and Michael Biehn begin to hug. In the shot where the Terminator begins to rise from the destroyed truck, look just a little to the right of Linda's head and you'll see a mans head pop up and his hands pull down on a lever that makes the Terminator rise up. (01:30:50)
Visible crew/equipment: When Sarah and Kyle have run into the factory, the Terminator is breaking through the armour plated door. As the Terminator comes through you can clearly see the two operator guys crouching behind the model. (01:32:45)
Revealing mistake: There is a shot from the Terminator's POV, before he rams the blue car with the semi truck, in which you can see that the car is already damaged. No slow-mo is required to see this, but it is a blink-and-you'll-miss-it shot.
Factual error: Right after Kyle saws off the barrel of the shotgun in the alley, he pumps a shell into it, then again after his dream of the future in the car, then a 3rd time in the night club before he shoots the terminator. The 2nd and 3rd time he pumps it, shells should come out. They don't. (00:35:22)
Revealing mistake: When the Terminator's flesh is burning off in the burning tanker wreckage, you can see the wire moving the Terminator puppet around. (01:29:45)
Continuity mistake: The telephone message left by Sarah's roommate changes the two times we hear it. The second time, there is no delay between "Hi there" and "ha ha ha fooled you", while the first time has a delay of over a second. (00:25:55 - 00:32:05)
Revealing mistake: During the final chase scene, Sarah loses control of the pickup and it rolls over, as it rolls you can plainly see that it has no engine. (01:26:05)
Revealing mistake: When Arnie drives through the police station, the cop is just sitting there. Not only that, his skin is a lot paler. It is too easy to see that it is a dummy. (01:00:00)