Revealing mistake: When Frank Bauggs is falling from the building, he is a very obvious dummy. His body limps around too much. (00:50:45)
Revealing mistake: A bunch of seedy individuals are gathered, weapons in hand. Unbeknownst to them, though, deadly ninjas are creeping by, with all the speed of fast-forwarded footage. The problem, besides how obvious the trick is, is that it also features a visible jump cut; you can see the foliage change position literally from one frame to the other during the same shot. (00:01:30)
Revealing mistake: When Donna destroys the helicopter, the cable holding it is visible.