Continuity mistake: When Pinkman and White are having breakfast in the diner, the items on the table keep changing in each shot. Specifically, the jelly, the milk, the cup with the cream and, most noticeably, the rolled napkin with the cutlery inside: Sometimes folded, others opened.
Continuity mistake: When Gus starts to walk away from where he killed Victor, he drops the Box Cutter, and we see it landing. However, after a cut to the next shot, its position has changed. It is no longer sitting on the line in the floor, and it is pointing 180° in the other direction. We can also see from Walt's shadow that the Box Cutter has moved quite a bit further away from Walt. (00:35:05)
Continuity mistake: During the diner scene when Jesse is eating, Walt asks him how he's doing. Jesse's head changes positions several times between shots. From looking out of the window, to back down at his plate, to back out of the window, to straight ahead again, all between shots.