(at around 1h 15 mins) When Jupiter and Pluto are running down the wash, just prior to Beast attacking Pluto, you can see a couple of equipment bags belonging to cast or crew sitting at the right side of the wash.
The goof items below may give away important plot points.
After the cannibal punks break into the family's trailer, Mars opens the birdcage, takes out the bird, snaps off its head and drinks its blood. Later, while Mrs Carter is being laid out on the sofa bed after being shot, the birdcage is clearly visible behind her, still closed and with the bird hopping around inside.
(at around 1h 21 mins) Toward the end of the movie, Bobby and Brenda use the left rear wheel of the car to pull Papa Jupiter across the ground, if the Axel had snapped like Big Bob said, this would be impossible.