Swaying Arm Ghost

The forearms and hands: The arms are the wooden dowels from old roll up blinds, but PVC or whatever you have will work. The hands are constructed from plastic packing foam blocks (from some random copier equipment). I twisted and forced a metal pipe (old tent peg) into the block to make the fingers and just cut a palm shape out of the block. Then used wire to build the hand and attach them to the dowels. (There are lots of ways to make hands, but whatever method you use, lightweight is what you're after.)

The shoulders and upper arms: I used a large jacket hanger as the shoulders. I straightened the hook and forced it up through the skull, a rubbery foam filled but fairly large one. (Any lightweight "head" will do really.) The upper arms are PVC pipes. All connected with wire.

Now for the "secret" or "trick" that gives it that random ghostly movement. The forearms are hung from one pivot point but with 2 lines (one on each end). Then the upper arms are connected in the middle of the forearms. This allows the arms to move back and forth in front of the body. "Restraining" lines on the ends, behind the ghost, allow for about 50 degrees of range and keep the "balancing" end of the dowel from swinging all the way around to the front.