Continuity mistake: This is right after Conner jumps down to the lower level to get to the grenade launcher and hurts his shoulder. He is crawling away from the T-800 and the shot is from right behind Conner's head. The T-800 is practically right on top of John, but when he shoots the oven and the molten steel lands on the T-800, the shot shows John like 30 feet away.
Other mistake: When Marcus, Kyle and Star are at the petrol station, a flying HK and the giant Harvester robot are able to appear just outside without making any kind of sound. In every other scene of the Harvester and the HKs however, they both make an incredible amount of noise.
Continuity mistake: In the scene where Blair escapes with Marcus and Barnes launches an explosive into the tunnel, Marcus hops onto Blair to save her from the scorching flames. After the fire, Marcus' coat would have been burnt to a crisp, his hair singed off and the skin on his back fried. More evidence pointing to this was that his coat was merely one previously worn by a Resistance fighter, not special in any way, and he has regular skin and hair.
Trivia: Reese's introduction isn't the only thing that stays the same about the character between movies. Here he uses his preferred weapon - a sawed-off shotgun. Marcus isn't keen on having a gun aimed at him though, so he snatches it out of Reese's hands, then teaches him a trick to keep that from happening - fashioning a safety strap. Reese puts that same trick to use after he steals a police shotgun in The Terminator.
Trivia: When Marcus Wright, Kyle Reese, and Star leave Los Angeles, they make their way up the hill up to Griffith Park. This is an homage to Terminator 1 because this observatory location is the same location that Arnold Schwarzenegger arrives at from the future, finding Bill Paxton and some other thugs and stealing one of their clothes.