And the size of the Lua runtime is nothing short of beautiful. I have yet to find a use for Lua though, so I'm still waiting for an opportunity to work on something with it.
I find it's used a lot in places you wouldn't expect. I found it used in a car radio, the modem used in my house, and a few other places. It's lightweight if you want to use it on embedded systems (for example, NodeMCU) if you're into that kind of thing.
I'm using it at work to parse SIP messages (with LPeg) for one of our customers (one of the cellphone carriers). Between LPeg for parsing, and coroutines in Lua, the code is pretty easy to read and follow.