For the past nineteen months or so, ever since I started working on Flex 2.0, I've been using JavaScript syntax highlighting for ActionScript 3.0. That's like using C syntax highlighting for C++! So today I decided to write a Vim syntax file for AS3, based on the syntax files for JavaScript, Java, and C#. Here it is: actionscript.vim. To make it work, just copy the file to your $VIMRUNTIME/syntax/