OSX 10.8: Open Apps from unsigned developers

With Mountain Lion's default Gatekeeper settings, when you double click an app that isn't signed with an Apple developer ID for the first time, it won't allow you to open it.

The solution (other than changing your security settings) is to right click on the app and choose Open from the contextual menu.

It still warns you that the app isn't signed but gives you the option of opening it anyway. You only need to do this once per app.