While our Lucy has her uses for kitty litter, there are others. When you get ice on your walkways, kitty litter is good for putting on anti-skid protection. It doesn't harm the grass like rock salt or calcium chloride do (no mattter what the manufacturers say). It usually runs right off with the melting ice.
As I said, you can also use it to represent rocks and gravel on dioramas, or as a base for finer particles, like sand.
Please note that I use unused kitty litter for these uses. But I am happy that someone now has found a use for used kitty litter. LOL