It would be nice to have a toggle option when building that disables an objects ability to cast shadows, particularly in sunlight.
Use case: I spend most of my time in a skybox. The skybox is large enough that I have a house and garden area inside it and for privacy reasons it is surrounded by walls that are opaque on the outside.
Because the walls are opaque on the outside they cast shadows on everything inside the skybox. Lighting is therefore slightly overcast even if the environment is otherwise set to be bright and sunny.
It would be nice to set the surround to not cast shadows so that I can enjoy proper day / night cycles in my skybox without having to derender or otherwise do away with the surround.
From a purely VFX standpoint I'm sure there are other reasons you might want an object that's visible but does not cast shadows - giant holographic statues, ghost ships, etc.