I've had some for years but never really known what to do with them, so now I've started experimenting with them.
A packet of those plastic ice cubes from the pound shop...
then Sharpie them up!
With every cube a different face.
Eventually I took the water out as they were too heavy to stay stacked properly, then used double sided tape to keep them stacked.
Stay tuned for more experiments with a loaded Sharpie!