Don039t Forget About Automator
It's a mature tool now, that has a huge amount of power. I often forget about how easy Automator is to use and set out writing Python or AppleScript when Automator provides a solution in a few clicks. Many times it's a one-off solution that I don't even bother to save.
Here's an example I used tonight to convert a folder of .md and .mmd files to plain text files and also set their default application to Byword (Thanks for the recommendation Brett).
