In the scene where Walter is drinking orange juice after having cooked, the right ear stem of Walt's eyeglasses is about an inch above his ear. When the camera cuts away to another view, his right ear stem has moved down an inch to be directly above his ear.
After Tuco beats Gonzo to death at the end of the episode, No-Doze drags his body back to the SUV, leaving obvious drag marks on the ground. In the subsequent shot, the drag marks are no longer visible.
The actors playing Gonzo and No-Doze have their characters mixed up in the credits.
When Walt was talking about drinking, he says that in 1930 they would have been breaking the law. There were no rules against drinking during Prohibition, only the sale and distribution of alcohol. Besides, Prohibition only ended in 1933 so saying it would have been legal a year later is doubly incorrect.
When Walt and Jesse drop the drum of chemical down the stairs it is obviously empty.
In the previous episode, Walt shaved his head when he discovered he had started losing his hair due to the chemotherapy, with bald spots at the sides visible. During the school meeting and afterward, you can actually see his head is just shaven but without any bald spots.
In the scrapyard when Walt is waiting with Jesse for Tuco, there are two light reflections visible in Jesse's sunglasses when there should be just one from the setting sun.
When talking about melting the lock to gain entry to the chemical warehouse, Walt says that the Nazi rail gun the "Schwerer Gustav," could not be destroyed by bombs, and in the end was destroyed by one man who parachuted in and melted the gun. In reality the Gustav was probably destroyed to prevent its capture. After the siege of Leningrad it was moved back to Germany and not seen again until Allied soldiers discovered it, destroyed, in eastern Germany.