Continuity mistake: Arnold goes to the gay bar to solicit the help of the guy he saved at the beginning of the movie. The guy is wearing a white shirt and a vest black/gold lamay. During their conversation he takes off the vest, then it cuts to another bartender. When it cuts back the guy has the vest on, another shot and the vest is off again.
Continuity mistake: Arnold dives to save the girl under the lid of a fridge. When all the drill bits are shot at him with his hand above the fridge door, none hit his hand. But in the next angle one penetrated his hand. Then in the next scene, when he's driving the van with both hands and when he swipes the credit card the wound appears and disappears.
Continuity mistake: Arnold is handed an upside down photograph of his friend's witness. As he views it the photograph is correctly oriented without being turned around.
Revealing mistake: When Arnie jumps from the plane, notice the stunt double. He weighs about half of what Arnie would, and has no muscles.
Visible crew/equipment: When the warehouse has collapsed on Arnold and he is coming out from underneath the rubble, you can see a guy "hidden" behind some tubes, wearing protective eye wear and holding a welding rod to make a shower of sparks (he is only visible in the widescreen DVD version).