While Gus is talking to Walt in the desert, Walt's glasses alternate between the earpiece lying on top of his right ear, and riding higher on his temple.
Ted removes a check from his checkbook and hands it to Skyler. It has ragged edges at the top. Later, Skyler holds up the check and the top edge is not ragged.
While Jesse and Brock are playing video games together, Jesse's controller is for an Xbox 360 while Brock's is for a Sega Dreamcast.
When Walt is in the crawl space and screams (at around 44:31 mins), you can clearly see a stack of 50 dollar bills ripped open and they are all blank pieces of paper.
When Gus visits Hector at the nursing home, you can see Giancarlo Esposito's mic transmitter bulging through the rear of his sport coat at the waist line as he pulls a chair over to sit near Hector.
Skyler and Kuby both tell Beneke to write a check to the I.R.S. This is incorrect. The check would be payable to The United States Treasury.
Saul mentions that Walt is wanted by the law, but he isn't since no one in law enforcement (besides Saul) actually knows he's Heisenberg.