When Rumbo is dropping nuts on Fluke's head in the very end, Fluke's paws keep moving between shots.
When the graveyard Night Guard padlocks the gates closed, locking in little Brian Johnson, the keys can be seen glinting as they dangle from the padlock as he walks to his truck. In the next view from outside the gates the keys are gone as he drives away.
When the wife is in the bathroom after her shower and Fluke is looking at the ring on the table, she puts the ring on, then looks at Fluke. The ring is still on the table in the next shot.
You can easily tell that the snow at the end is fake.
There isn't very much glass after Jeff's crash considering the whole windshield was broken out
In the uncut version when Fluke pees on the animal shelter employee you can see the tube between Fluke's legs where the liquid is coming out.
After Brian's mother tells Fluke to come with them in the cemetery, the shot cuts to Brian in the car and then back outside. In the bottom left hand corner, you can see a person kneeling there.
When Fluke has seen his wife and kid he follows the car. When he arrives at their house he runs towards the door as he's running across the grass a shadow of someone is visible.