I've used Lua extensively. I wrote a tool at work to do packet analysis in Wireshark which has a Lua API. I've written a couple of simple games using the Love

I've used Lua extensively. I wrote a tool at work to do packet analysis in Wireshark which has a Lua API. I've written a couple of simple games using the Love2D framework. I once wrote an IRC bot using luasocket. I started to write a debugger which was an amalgam of C and Lua, but I've since abandoned that project (not because of Lua, but because I lacked the free time and the patience to support more than one object file format). I also experimented with using Lua as a target for a Clojure-like Lisp dialect. The compiler is itself written in Lisp and compiles itself to Lua. I've written an Asteroids clone and some toys in Lisp and compiled them into Lua. It's a very fun language to program in. The reference implementation is also small enough that you can reasonably expect to know its ins and outs in about a week. The C API is really nice; it makes embedding in C a breeze. LuaJIT itself has the best FFI I've ever seen: you can practically #include a C header file in your Lua and it just works.