Revealing mistake: As Bunk is ordering ballistics to rush comparisons, the dead bodyguard is breathing during the scene. (00:01:55)
Other mistake: When waiting at Lake Trout to ambush Marlo, the Barksdale crew are in the same car that Marlon was driving round earlier in the series (same number plate: 107M703) It is visible as they (Avon and his crew) drive away from the scene after Chris has shot into the car. (00:51:02)
Revealing mistake: At the start, while looking over the corpse from a ground level shot, the corpse is dressed differently from the overhead shot, and is very obviously breathing. (00:01:50)
Reformation - S3-E10
Visible crew/equipment: During the opening sequence when two hoodlums are walking out of the convenience store, a lighting rig and crew can be seen on the right-most part of the frame. (00:02:15)
Back Burners - S3-E7
Continuity mistake: When Poot first jumps up after Snoop rakes the corner, the blood stain his shirt has absorbed is much larger, and singular - consistent with lying in a pool of blood not coming from your body on a flat surface. When the frame changes, there are now three blood stains, each much smaller. (00:51:52 - 00:52:56)
Chosen answer: As he's trying on his new hat, Valchek says, with a smile, "fits like a glove!"