Last year, there was a very popular challenge to create an image containing every 24-bit RGB colour.
My challenge is to create a smooth animation (24 frames/s say), where the colour of every pixel of every frame is unique. I will also allow duplication of colours as long as every colour appears the same number of times (greater than 0), since otherwise the animation will have to be short, or the frames small.
I have produced some examples here, based on the winning solution to the 2d version. Unfortunately, it seems you can't embed videos, so links will have to do.