Super easy robot arm build. I built this to hang on a half mannequin torso, but you can attach it to anything. This build is not complicated, Using #4 screws and nuts, and MG996R servo. If you use an Arduino, a simple sweep effect using multiple servos works great. For specific movements, I used Bottango.  Build Tutorial HERE: 

Servo Base Connector>Servo Arm Shoulder Base>Servo Mount>Left Servo Shoulder>Left Servo Shoulder Bar>Servo Shoulder Bar