According to Unity documentation:
On Mac OS X PlayerPrefs are stored in ~/Library/Preferences folder, in a file named unity.[company name].[product name].plist, where company and product names are the names set up in Project Settings. The same .plist file is used for both Projects run in the Editor and standalone players.
So you want the file "unity.Calitarus GmbH.Black Forest.plist" - but unless you have a plist editor, that's not helpful. :-(