Terminator 2: Judgment Day (1991)

Revealing mistake: When John Connor and the Terminator are at the payphone calling his step mom, the Terminator punches the phone and puts a massive dent in it and change comes out. If you look at the bottom of the phone before he punches it there is already a dent there. [Pan & Scan version ideally, although you can just see the very top of the dent for a few frames in widescreen]. [ALSO- you can see that the area where Arnie hits the phone is merely plastic, which is unpainted to match the black phone!] (00:40:00)