Continuity mistake: During the chase, we see that there are only three cops (we see a head-on shot of the three cops with an empty sidewalk behind them), but when Mr. Pink opens the car door and starts firing in the direction of the cops, the first three cops (the thin ones) scramble back around the corner. Just then, a fourth cop (the fat one) pops around the corner from nowhere and gets shot.
Other mistake: During the post-robbery flashback where Mr. White has just killed two police officers, there is a shot of Mr. White saying, "Let's go." after determining that Mr. Brown is dead. As Mr. White & Mr. Orange leave the scene, you can see 3, maybe 4 men standing perhaps 20 feet away, lounging in front of a dark blue truck. For all the car-crashing & gunshots easily within earshot, those witnesses seem awfully nonchalant.
Continuity mistake: During Mr. Pink's flashback, he's chased by three cops across the sidewalk of a long, straight avenue - apparently, they all pass the same exact spot numerous times. Notice the white van parking next to the sidewalk as the policemen run next to it - it is followed by a yellow truck. Look closely beneath it, and you'll spot a place where the sidewalk mixes with the road. Later on, in the wide shot of Mr. Pink running, he passes next to the same exact white van, and the same spot where the road mixes with the sidewalk is visible just next to it, right as he picks up the briefcase behind it, yet the yellow truck is gone. Since the cops are behind him, that place should be far away, as he's been running along a long avenue. [To make the street look longer, the filmmakers shot the chase a few more time on the same short street to make it look like a long avenue. Yet the white van marks the same spot, and thus it is a mistake.].
Continuity mistake: After the climactic shootout near the end of the movie, Mr. White falls on his elbows, facing Eddie's body. In the next shot, Mr. Pink leaves. When he is leaving, Mr. White is facing the back of the warehouse, where Mr. Pink hid. That is a near 45 degree turn when Mr. White was in both shots.
Continuity mistake: In a scene near the end, Joe arrives at the warehouse and tells everyone that Orange is the informer. We frequently see Orange on the floor, however the blood patch he is lying in changes from wet to dried to very wet to larger and smaller and back and forth. Also sometimes there are bullet casings around him or the magazine he dropped depending on the shot.