During the opening credit sequence, Ryn (Clint Glenn) prepares to inject himself by squirting some liquid out of a syringe. This is done to clear the syringe of air bubbles, yet when he injects himself, there is a large air bubble in the syringe.
The goof item below may give away important plot points.
Just after Ryn has been bitten by a Zombie (when he wakes up after being shot) and has stabbed it, he leans on his bag to get up. He has just been bitten by a zombie yet there is no bite mark on his arm.