Green Screen Props
Avatar used a subtle specialized version of props. Most of the props used were created as green screen objects or sensors for the green screen.
While computer animators can create almost anything in Maya and other 3D programs, actors still need something to interact with.
Classic Props
But then there are the classic props used in most, if not all movies. Great time and effort can be put into them, or they can be put together quickly depending on what they are needed for.