Common Names
aka buzztail, buzzworm. Crotalus atrox

Habitat
desert foothills, rocky outcrops, shrubland, dry sandy washes

Description
generally colored a shade of dark or light brown. Its pattern is a distinctive row of large, dark diamond shapes edged in yellow trim, running down the length of its body. The diamonds fade to dark rings around the tail, where the distinctive rattle begins. A dark stripe edged in yellow runs back from the mouth to the eyes on each side of the head. There is no significant difference in appearance between males and females except that males are generally larger. They grow to an average length of 4½ feet, but can reach a maximum length 6½ feet.

Source
Wikipedia

Comments
Most common encountered snake in the AZ desert terrain.