The Specialist (1994) - 10 mistakes
Continuity: When the men go up to Stallone's hotel room, you can see them going down a long passage and passing a few rooms before coming to his door. But when the room blows up, the shot from outside the building shows nothing to the left or right of his room. What happened to the rest of the floor?
Factual error: In the first few minutes, right before the explosion of the car with the little girl, Stallone is running like mad to disarm the bombs (on the pillars of the bridge). However, he isn't fast enough, and the last bomb explodes. The trick is that the bombs are just chunks of TNT, planted about eyeheight, but when the bomb explodes, the flames and stuff go upwards (not reaching/hurting Stallone, who is about 3 meters up and at the exact height of the last bomb).