An Urban Terror .cfg in TextMate on OS X

You can use any plain text editor you like to create/edit .cfg files, but some are better for the task than others. The following are recommended editors for Urban Terror/Quake3 config files.

Name License Description
Sublime Text Paid A feature-rich, cross-platform editor, but paid and closed-source. If you can afford it, Sublime Text 2 is well a text editor worth the money.
Notepad ++ Free, Open-source Includes a robust package manager that can download and install extensions easily, including syntax highlighting for ini/cfg files (which will require some customization on your part). Otherwise, a Quake3-style config language definition is in development.
Kate Free, Open-source Free and feature-rich. Includes syntax highlighting and Vi-input mode. It's the perfect editor for those just getting into the world of programming, as you'll quickly discover all the awesome features an advanced editor has to offer without feeling overwhelmed and confused.
Mac OS X
TextMate Paid, Open-source Although technically a paid program, TextMate is open-source now and you can download and use it for free. There is an optional bundle you can download after installing TextMate for Quake3-style configs (syntax highlighting). All bundles are also open-source and editable, so you can easily customize how syntax highlighting works for you.
TextWrangler Free This is the "little brother" to the paid app BBEdit. BBEdit includes all sorts of nice features, but you don't need any of that for editing Urban Terror configs. TextWrangler does not include syntax highlighting for Quake 3 configs, but a downloadable language definition is in development.