Can you believe that MS Entourage 2004 still cannot play select System Sounds found in System -> Library -> Sounds or ~Library -> Sounds without the assistance of a third party app and an AppleScript for each and every sound? If you're like me, you've got hundreds of available System Sounds, and you get really, really tired of making a new 'Play Sound' script for each sound you want to use in Entourage (or Mail).
The following script is designed for Entourage, but can easily be adapted for use in Mail. It has only been tested in OS X 10.3.3 Panther and Entourage X, but it should work in older versions; the key is that you have the scriptable Script Editor and the Play Sound application.
Download the compiled script here.
[robg adds: Due to the length of the script, I haven't included the source here. However, I've also mirrored the file on the macosxhints.com server. Instructions for using the script are included in the comments at the beginning of the script. I haven't tested this one.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040514091142145