When Adam confronts the vampire group in the sewers, he decapitates one, killing it. However, when the body falls to the floor, followed by the 'decapitated' head, the previously-fallen body clearly has a head attached.
After Willow, Tara and Buffy (as Faith) arrive outside the church, Willow starts talking to the cop but we see her face in the corner of the screen and her mouth clearly isn't moving.
When Willow, Tara and Buffy (as Faith) arrive outside the church, the camera crew are visible in the trucks windows and shiny paint.
At 33:07, as "Buffy" enters Giles' apartment, you can see part of a lighting flag at the top of the frame as the camera tracks Giles across the room.