One of my Christmas presents is one of the most unusual items I have ever played with. It is a product of Sweden called Kinetic Sand and it fascinates me. Playing with kinetic sand is a near magical experience. This stuff has its own motion and flows like water through your fingers. You don't have to wash your hands because none of it is left on your hands.
I can shape it into all kinds of shapes that feel solid and even hard but squeeze it and it crumbles and flows like a liquid. It is mesmerizing and relaxing. I think I will be playing with it a lot this year.