Other mistake: When Bishop kills the arms dealer while Steve McKenna looks on, he stands behind the guy and in one quick motion, rips off the belt cleanly from the guy's waist, then he strangles him with it. There is no way you could yank the belt off like that if it were buckled. And even then, the buckle is certain to snag or rip one or more belt loops before you can pull it off.
Other mistake: When Walter Farris drives up in his DEA pickup, it has California plates and not federal GSA plates.
Other mistake: Towards the end during the last fight with Zeus, Atom is following Charlie as a mirror - when Charlie moves his right hand Atom moves its left, etc.. At one point in the last round Charlie jumps and punches with his right hand, but Atom hits Zeus with its right too.
Other mistake: When Martin Harris is being chased in the taxi, paint covers the entire screen. Martin asks for the wipers to be switched on, but by the time the taxi crashes, the windscreen is completely clean, with no sign of the paint. There would be wiper marks and the remaining paint on the windscreen.