When working with ArcScene and ArcGlobe, it would be great to have a navigation box with standard views (Top/North, Left/West, Right/East, etc...) to be able to "snap" to default views. This is achieved in Autodesk Revit software among others.
Also, to have a "slider" of sorts to show the time of day, but to have it represented graphically. These ideas are used by Autodesk and are simple yet effective ways for the 3d interface to be improved.