 When you're able to move with six degrees of freedom and look at all directions, oftentimes the things that you need to pay attention to are off-screen, so way-finding becomes crucial. This example from Supernatural has some really great examples of various forms of way-finding. The objects you hit are shaped in the direction that you should hit them. The motion trails indicate which way you should move your hand controls, and the arrows coming off the objects help direct you to things off-screen. Even the triangles indicate a shape you should move your body into, and all of the UI elements are designed to fit very naturally into the overall experience.