Factual error: During the bank robbery, Hancock throws a metal lamp shade to sever the leader's hand, who is holding a spring loaded, dead man switch. The switch would have released the instant the hand was severed and the muscles relaxed.
Continuity mistake: After Mary reveals herself to Hancock, the next time she and Ray are at the kitchen table, the towel Ray picks up off the table immediately changes completely from the one that Mary uses to try and open the jar.
Other mistake: As Red goes to shoot Hancock, there's no bullets or shells in the cylinder.
Continuity mistake: In the board meeting, Ray holds up the Allheart presentation with his left hand. A second later, it's in his right. And he's moved further down the table. (00:13:20)
Factual error: When Hancock saves Ray's life by stopping the train, stopping the train instantly like that would have caused it to violently derail, likely killing everyone on the train, and causing massive damage to the entire neighborhood.
Factual error: End of the movie, Hancock is in New York with the sun setting. Ray and family are in L.A. with the moon out and no Sun. New York would have nightfall before L.A. would, considering it's 3 hours behind New York.
Suggested correction: It is nighttime in both locations. In New York, there is a dim glow in the sky due to light pollution. This the same reason it is almost impossible to see any stars in the night sky in New York City. Also, a full moon that far above the horizon is only possible at nighttime, and we see Hancock look up at the moon, so again it is nighttime in NYC.
Visible crew/equipment: As the camera looks at the female cop pinned down, the crane used for the high fly stunts is reflected in the car's finish.
Continuity mistake: As Ray gets done with the call with Hancock, his hand starts to drop. In the wide shot his hand is back up by his ear.
Visible crew/equipment: As the guys in the SUV look around, the studio lighting is reflected in their shades.
Visible crew/equipment: After waking up on the bench, Hancock puts on his shades. As he looks around, the studio light reflector is seen in his shades.