At about 37 minutes Timothy Olyphant shines a flashlight at a guy and has it held from below, a camera change and suddenly he's holding it entirely different.
At 14:22, a character checks a text message on his phone, and the screen displays a temperature of 16°C (61°F). However, the film is set in winter with snow-covered streets, which is inconsistent, as snow cannot exist at that temperature under normal conditions.
The characters use firearms that seemingly have unlimited ammunition, firing hundreds of rounds, even from handguns, without ever reloading.
Cars: When the camera pans over busy traffic in the streets of New York during the scene where Forest Whitaker's drives are shot you can see several cars that are not sold in the US or Canada such as a Renault Clio, Peugeot 208 and Dacia Duster.
At around the 1:07 mark, walker is talking to Ellie in the police station and Ellie is clearly wearing a normal tie as part of her uniform. As a police officer, she would not be wearing a normal tie as this could be used to choke the officer if someone was to get into an altercation with them and she should be wearing a clip on tie.