Safari Cleaner
App to automatically clear cache, cookies, etc. from Safari on quit
... Private Browsing on automatically on launch. Just launch SafariCleaner and select the items you want to clear on quit, simple as that!
Note: If you want to use the Private Browsing feature, you must go to System Preferences-->Universal Access and check "Enable access for assistive devices"
I hope you'll find this app helpful. If you have any comments, feedback about bugs, or feature requests, please post them in the forum. Thanks.