When Willie brings the stripper home and listens to his answering machine, the sound of a tape rewinding is heard. However, the machine is clearly a digital model, as revealed by a closeup during Marcus' call, and thus has no tape.
When Willie returns to the house with the stuffed elephant and is being chased by the cops, the bags of sand with the candles in them on the sidewalks are no longer present (he had just put them out before going to the mall).
Just before Willie wrecks the nativity donkeys in front of all the kids, he is shown collapsed lying down on the escalator with what looks like a broken bottle in his hand. In the next shot when he stands up and walks towards the donkeys the bottle is clearly whole. Then in the next shot it is broken again.
When Willie and Marcus go to the store and the security guard stops them it is 8:00. When Marcus is climbing through the vent, the clock on the wall says 9:05, and he is supposed to be doing this right after they got in the store. (Although, as always, the clock could be wrong.)
When Willie and The Kid run into the kitchen from when the he cut his hand, the faucet is turned on, then is turned off, then following shot shows the faucet is back on without anyone turning it on again.
In the beginning of the movie, when Willy is drilling the first safe, he has a cut on his right cheek - the same cut he gets towards the end of the movie. After he gets the money out in the beginning, the cut disappears.
While Marcus takes a candy cane from Bob Chipeska's desk, you can clearly see that there are three. In the next shot, there are four (after he took one). Also, the number of candy canes is inconsistent between shots.
When Willie is lighting the lights from the popcorn bags outside the house he appears to be lighting from his left to right. However, different shots show that all of the bags continuing down the street are already lit even though he didn't make his way down that far.
When Willie is hitting the safe with the slug hammer, it's supposed to be locked and secure. The second time he hits it you can see the door slightly open, but in the next shot it's closed and secure again.
When Marcus turns off the surveillance cameras, he uses one button to turn off the TVs. If he just turned off the TVs, then the cameras would still be recording (but the images wouldn't be displayed in the security room).
When Willie is trying to shut off the alarm clock, he presses several buttons. Occasionally, the alarm clock's display changes 12:00 and then back to 11:15, because he presses the "alarm set" button (which one would hold while setting the alarm). But he was awoken by the alarm going off, and the display reads 11:15, which means that the alarm shouldn't be set for 12:00.
The goof item below may give away important plot points.
When Willie is selecting the stuffed elephant for The Kid, he turns when he hears the sound of Marcus cocking the revolver he is holding. But when Marcus is talking and waving the gun around, the hammer is still forward and uncocked.