coroutines in lua a great for game development. Also the reference, luajit and one more commercial that I've seen are all based on Lua state object, rather than global data (python?).
And luajit is more alien technology than common lisp :)
It just works (for code written to Lua 5.1; it's about 95% compatible with Lua 5.2, which changed how modules work) and can pretty much replace Lua (either the standalone executable, or linking it as a library). The "alien tech" probably comes from how it works, converting Lua to native code. I can't say how difficult to understand, since I haven't really looked into the internals, but from what I understand, Mike Pall created a new way of looking at assembly language as part of LuaJIT.
It was a pun on Common Lisp (great language btw) - http://lisperati.com/logo.html
But then after seeing LuaJIT2 I think there was something even more alien. It made me understand that I don't know programming very well after seeing what Mike Pall did there.
And luajit is more alien technology than common lisp :)