Classic Compound of 3 Cubes plus One According Symmetry
I have no idea what the name of this model is. I got the idea to add to 4th cube myself, though I was of course not the first. This model is one of my favourites. It is simple, though it has some peculiar properties:
It contains 4 cubes, but only 3 colours.
Adding the fourth cube results in a model with less separate faces (24 less), and as a result it is easier to build.