Add an action to a SharePoint list actions menu for a specific list

If you have ever tried adding a SharePoint custom action to the actions menu and tried using "List" or "ContentType" as the "RegistrationType" and then tried to specify a specific list or content type in the "RegistrationId" you know that it doesn't work. SharePoint will silently not render your custom action. If you try and target a generic list using a "RegistrationId" of "100" you will see that SharePoint will gladly render your action on every list in the site. I have found a rather kludgy work around to the problem.