Other mistake: When Lewis looks at the cup that he got from the coffee machine, the cup has two Jacks and two Aces. When he looks at the bottom of the cup, it has a Queen underneath giving him two pairs, but he tells Gwen the receptionist that he got a full house.
Continuity mistake: When the T-1000 throws the driver off the truck and chases John's bike, the buildings on the right are a brown parking lot and a modern white building. In a couple seconds, the truck keeps swapping from being by the middle of the white building or way behind, next to the brown parking lot approaching the white building. The position is inconsistent many times.
Revealing mistake: In the scene when the T-800 first comes through the time machine, in the shot where he stands up. If you look towards the right side of the bowl shape that's melted into the ground, you can see that the bowl shape is actually above ground. There's a shadow being cast by it on the right side. (00:06:30)
Continuity mistake: The T-1000 has the gun holster on his left side and takes the gun out with his left hand when the guard in the psych ward hits the alarm. A few scenes later when the T-800 (Arnie) asks Sarah to 'come with me if you want to live' the T-1000 walks through the cell doors, the holster is on the right hand side and the gun in his right hand. (01:10:00 - 01:12:00)
Continuity mistake: After the first fight in the steel mill, as the T-800's arm ends up in the gear the black glove on his left hand is torn in many places, revealing parts of the endo-skeleton hand. However, later when the T-800 frees himself from the gear, he is wearing a black glove with no tears on his left hand.
Revealing mistake: After the Terminator has jumped on to the truck and shot the T-1000 full of bullets he pulls the wheel to the right so that the tanker truck skids and falls but if you look closely you can see that the stunt double for the T-101 merely fakes he's pulling the wheel, and then holds onto the cab and you can see the stuntman for the T-1000 inside the cab turning the wheel before it flicks to the wider shot. (01:48:10)