The Ithaca 37 is a pump-action shotgun.
After Kyle Reese fled the clothing store, he opened a police car with no one in it and took out an Ithaca 37 shotgun. Later, he used a hacksaw blade to saw off his shotguns stock and he tied a string onto the guns grip while tying the other end to his shoulder to keep it in place when he hid it in his coat.
Kyle carried his shotgun to Tech Noir where he tracked Sarah Connor in order to prevent the T-800 from killing her. Kyle, not knowing what the T-800 looked like in its living tissue disguise, had to wait until the T-800 walked towards Sarah in order to "Zero him"
As the T-800 loaded its .45 Longslide and aimed the laser point Sarah's forehead, but Kyle quickly pulled out his Ithaca 37 and fired five rounds at the T-800, disabling it for a few seconds. The T-800 attempted to kill Kyle with its Uzi 9mm, but he was fast enough to dodge the shots. Once the T-800 reloaded its Uzi and was about to shoot Sarah, Kyle jumped out from behind the T-800 and shot it five times again, blasting it away and crashed though the bar's window.
Sarah and Kyle fled from the bar with the T-800 chasing them. While Sarah was near Kyle's open car, Kyle fired 2 rounds at a car at a distance, thus blowing it up with the T-800 near it, resulting in its hair burnt and eyebrows singed off.
A while after, the T-800 stole a police car to peruse Kyle and Sarah. It fired a shotgun, attempting to kill Sarah while Kyle fired his shotgun at the T-800. Kyle damaged the T-800's flesh with his shotgun and then the T-800 crashed into a wall with Kyle and Sarah crashing along with it. The police surrounded Kyle and Sarah as well as the empty police car stolen by the T-800. Kyle was going to exit his stolen vehicle and kill the police with his shotgun, but Sarah stopped him from doing so.
It is presumed that Kyle's Ithaca shotgun was confiscated by the police after he was arrested.