I tried to contact 'Wes' about the Lua bundle mentioned on the Wiki bundle page, but never got a response, and decided to just write my own.
I think the syntax highlighting is correct - it includes appropriate highlighting for all the keywords as well as all the built-in library functions.
In addition to some convenient Snippets for code forms that I personally write frequently, I've added 'cheat sheet' Snippets for all the global built-in functions and the table, string, and coroutine libraries. These tab trigger Snippets fill out the argument list with descriptive names, including which parameter(s) are optional. When parameters are optional, I included the preceding comma in the placeholder, so that tabbing through the function and pressing delete will remove any undesirable optional parameters.
(I got tired of entering all the Snippets, and have not yet added Snippets for the math, os, or io libraries.)
You can download my bundle from http://phrogz.net/tmp/ Lua.tmbundle.tar.gz
(Is anyone else using programming Lua on MacOS X? :)