My concrete ball. I actually made this last summer at work during a lunch break and rediscovered it while unpacking some boxes today. The concrete I made it from is the quick-set type that you just add water to. I had some left over that would have gone to waste, so at my friend's suggestion I made a ball by compressing and rolling it in my gloved hands until it was as round as I could get it. It's not quite perfectly round, but I still like it. It's like holding a little tiny planet in the palm of my hand.
The penny is just there for a size reference.