Labs

Here's one you've already got. Script Editor is Mac OS X's bundled AppleScript Editor, found in the Applications > AppleScript folder.

It's perhaps the least-designed application Apple has ever shipped, consisting only of a two-pane window and five buttons. In many ways it was a forerunner of Automator, and although that application is great for the beginner, you can't beat raw AppleScript for true power.

It uses plain-English commands, such as tell application and display dialog, meaning that it's quick and easy to learn, and because all of the commands and their attributes are colour coded it's easy to diagnose problems in your scripts.

The most common OS X applications, including those bundled with the operating system and stalwarts like Word and Excel, include AppleScript Dictionaries, allowing you to expand their featuresets. For those latter two, this is particularly relevant since Office 2008 dropped Visual Basic support.

Its only main drawback is its tight focus on AppleScript, making it far less versatile than alternatives seen here.