Tumblr's Confirmation Modal
Tumblr uses a confirmation modal to educate users on the repercussions of deleting a page. Here's what it looks like:
What we like: firstly, the text here is awesome. Clever, funny, and seemingly appropriate for the general tumblr audience. Secondly, this confirmation modal requires a CTA that involves typing in a username and password, rather than simply clicking a button.
Something to note: we aren't really sure if it's good or bad, but the decision to implement a full-scren takeover, as opposed to a transparent-background modal window, is definitely noteworthy.