How can I block Facebook app and game invitations once and for all?

People keep asking, so here goes the answer:

You can block app invites from specific friends from Privacy Settings » Manage Blocking » Block app invites, and you can block specific apps from Privacy Settings » Manage Blocking » Block apps. If you do not use any Facebook apps or games and want to block them all from seeing any of your information or sending you invites, you can turn off Facebook Platform completely by going to Privacy Settings » Apps, Games, and Websites and clicking Turn off all apps.