I was playing with my LEGO Mindstrorm Nxt when I build this humanoid. It doesn't use any motors though. But it can help being a model.
This used up lot of pieces, so you might need to be ready for it (not quite many actually)
Step 1: Make the arm
The arm, forearm, and crab hands are shown here. My model isn't perfect because it doesn't have any head and proper hands. But, just go ahead.