This is a collection of Proactive Dialogs, more will be added soon. Proactive dialogs help the user along in the experience by giving them meaningful feedback when a user does something that can create, modify or delete valuable information. With a clear message, Proactive Dialogs are a user's best friend when they are in danger of doing something that can not be undone. A common pattern includes having to type in a confirmation word or phrase. These dialogs come in the form of a modal, disrupting the user experience to communicate the importance of the action being taken.
Github does a masterful job of communicating consequences to user actions.
Along with an incredibly well designed interface, MailChimp does a great job of communicating loss of data warnings.
PayPal shows a nice alert when you remove a bank account.