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Nightmare Fuel: Wolfen
It's abundant in the film. The wolves can pop up from anywhere at any time. This is much more apparent in sequences where the wolves are out of view and are killing people.
The sequence where the zookeeper is on his motorcycle and he can hear the wolves all around him and he's trying to get away. He goes through a tunnel and you think he makes it when a wolf comes out of nowhere like a rocket and knocks him off the motorcycle.