Visible crew/equipment: At the very end of the episode, right after he tells Jesse how he used the red phosphorus to kill the gunmen, Walt leans down to vomit. You can see his microphone transmitter under his shirt. (00:54:20)
A No-Rough-Stuff Type Deal - S1-E7
Visible crew/equipment: When Tuco is beating the other thug to death, the camera pans first on Walter, then Jesse. When it is on Jesse, the entire crew can be seen in the reflection of his sunglasses. (00:45:35)
Visible crew/equipment: Just as Walt is saying the line about checking to see if the other one is dead in the RV, the edge of the set comes into view very briefly on the right hand side. (00:15:10)
Cancer Man - S1-E4
Visible crew/equipment: When we see a close up of Jesse stamping on the spliff you can see an orange marker on the floor where Jake is stood. (00:42:20)
Visible crew/equipment: When Walter talks with Jesse outside the Mesa Credit Union, just after giving him the money to buy the RV, a boom mic pole can be seen reflected on Jesse's car door. (00:36:12)
...and the Bag's in the River - S1-E3
Visible crew/equipment: At the start when Jesse looks over his shoulder at Walt, a stage light and what appears to be a light screen are reflected in his mask. (00:02:00)
Visible crew/equipment: At the very beginning of the episode where the RV crashes against a rock in the middle of the desert, a camera badly hidden behind a bush can be seen on the right side of the screen immediately after the crash. (00:00:57)
Visible crew/equipment: When Walter puts the mask over Jesse's unconscious face after drugging Emilio and Krazy-8, in the POV shot of Jesse where the camera is looking up at Walter, the reflection of the camera can be seen in Walter's mask. (00:51:05)
Chosen answer: It is part of the ritual for la Santa Muerte. It is a sign of humility and sacrifice.
djm