Continuity mistake: When Travis is with the gun salesman, he is trying out the black gun. You see a close up shot of him holding the gun with his arm outstretched with his jacket on. In the very next shot (no time has elapsed) his arms are at his side and his jacket is now completely off. (00:56:50)
Continuity mistake: While De Niro is talking to Jodie Foster you can see a bus out the window. When the screen switches to Jodie Foster's view you can see the same bus driving, but then it changes back to De Niro's view you see the same bus driving up to the window again. This keeps happening throughout the scene, the bus keeps driving around the building.
Continuity mistake: When Robert Deniro shoots the pimp's hand off in the hallway (shortly before shooting Sport the second time), blood splatters on his face, across his left eye and forehead. As he stumbles up the stairs (still shooting the handless pimp), the blood has changed, and finally in the shot where Deniro pantomimes shooting himself, the only blood on his face is on his chin.
Visible crew/equipment: In the scene where Robert De Niro shoots Sport the pimp in the stomach, the bullet supposedly goes through Sport's back, and blood splatters onto the doorway framework behind him. However, as Sport falls to the ground, look closely, and you can see a wire dangling from his lower back, which was used by the special effects team to detonate the fake blood packet. (01:39:05)
Visible crew/equipment: In the scene right after DeNiro is watching the Senator on the TV, he is driving in his cab past the campaign headquarters. As the camera goes past the window and focuses on desk phone, you can see the reflection of a cameraman for a second or so in the glass.
Continuity mistake: In the scene where De Niro shoots and kills the man robbing the convenience store, the clerk takes De Niro's gun off of him and starts beating the already dead body with a pole. If you watch the scene carefully, the dead body changes positions contrary to how the man is hitting him. Clearly the scene was shot several times with the dead body being placed in different positions.
Continuity mistake: During the same scene there is a white van parked across the street behind De Niro. Then it's gone. Then it's back.
Other mistake: There seems to be no bullet impact into the wall or near Murray Moston after the .44 Magnum revolver is discharged. Given the general direction and angle the weapon was pointed, a bullet should have blown out part of the wall near Murray Moston.
Character mistake: When Travis is buying guns, Easy Andy (the gun salesman) makes a few errors. Firstly, he states that the Smith and Wesson 61 Escort is a "Colt .25 Automatic." Secondly, he calls the Astra Constable a ".380 Walther." And lastly, he talks about the ".380 Walther" saying "during World War II, they used this gun to replace the P38. Just given out to officers." This is also incorrect.