While David drives off from the garage the driver's mirror takes a shot from the mobster and is damaged later on when you see a close up of David driving the mirror is in perfect condition.
When the mobster is trying to drive away from the Hulk in the silver car you can see the driver's side mirror is damaged, on the next shot just as he starts to drive away it is in perfect condition and when the Hulk hurls the engine block at the car it is broken again.
After the Hulk knocks over the large gas pump labeled Eagle Flying Service it inexplicably disappears in later shots.
When the blue car drives past the 10 miles to Flagstaff sign you can see the rear fender is still on even though the hulk had tore it off before.
When the mechanic's car takes off from the gas station lot the tires squeal, but they are on dirt.
Reflection/shadow of boom mike in window and on wall behind David and Nancy at the bus station.