Continuity mistake: After Pinkman opens the bags filled with money he throws his gun along the floor. When it stops it points in a 3 o'clock position. When the angle changes it points in a 1 o'clock position. (00:41:00)
Continuity mistake: In Season 4 we see Mike gets shot in the ear and and has a flap of flesh hanging off. In this episode, there are no marks or deformities on his ear.
Chosen answer: It is part of the ritual for la Santa Muerte. It is a sign of humility and sacrifice.
djm