Huh?

If you were as confounded as I was when Redactor's default font switched to Trebuchet, install this little bugger.

How?

Download the repo (that green button in the corner), rename the folder helvetica, and drop it in craft/plugins.

Alternatively, add it as a submodule:

$ cd path/to/your/craft/project
$ git submodule add https://github.com/AugustMiller/craft-redactor-helvetica.git craft/plugins/helvetica

…then jump into the admin and enable it!

Ugh

I know, this is ridiculous. If you've got a project-specific plugin, you can basically copy the contents of the init method of HelveticaPlugin.php into your own plugin, then drop in styles.css into its resources/css directory.

🌳