Near the beginning of the movie, when Nick realizes he's totally blind and keeps calling out for his partner, Frank, Nick can be seen sloshing through a trough and reaches his right hand out to grab a tree to steady him. How could he see the tree to grab if he was totally blind?
During the van chase where Nick is driving the van, at one point you can see through the rear view mirror (before it gets shot off) that they just passed the "Reno: The Biggest Little City In The World" sign, but just a moment later (when Nick runs through the red light) you see the big sign coming up ahead.
Immediately after Nick's scenes in Vietnam, he is seen walking down a stretch of highway signed as Florida State Road 84, which is shown as a 2-laned stretch of road. At the time of this movie's production (1988-89), the real SR-84 had already been upgraded to a 4-laned divided highway (just prior to becoming part of present-day Interstate 75).
During the van chase when Nick is driving, Billy accidentally tells Nick to turn right onto supposedly a one-way street, however as they drive down the street, you can see traffic lights on both directions. One-way streets would never have traffic lights facing both directions, and this particular street was obviously a two-way street re-painted to look like a one-way.
When the policeman gets his hand sliced off and it falls to the floor, you can see a white wire going from the back of the hand into the floor. This wire is what creates the shot from the gun that the hand is holding.
The goof items below may give away important plot points.
At the end of the movie Randall Tex Cobb gets stabbed in the stomach by Nick's sword. He pulls it out and drops it on the floor. In the next shot when we see him crawling along the floor the sword is gone. Then it's back again when the boy runs over and picks it up.
While Nick and Slag are fighting each other, we see Frank and MacCready fighting for the shotgun on the floor, but after Nick cuts Slag in half and he falls off the cliff, it immediately changes to the scene where everyone is in line to board the bus. How were they able to subdue MacCready and what happened to him?