Mechanical and magnetized movie robot "The Iron giant". You can hit him and maybe it will re-assemble himself like in the movie !? You have just to buy some screws and neodyme magnets, thread some parts and 3D print, it's easy and children will be very happy !
PLA, 10% honeycomb Infill, 0.4 Nozzle, and some supports for legs only. Don't forget to realize mirror foot and legs to be symetrical and perfect.