Have a paragraph style call a master page
Particularly useful if preparing a book with chapters. This would allow the opening page of a chapter to use a different master page than the rest of the document. Then, if the book is edited and the text reflows, chapter starts would still have the correct master. I can think of other uses, such as when an image is designed to bleed off a page and you don't want the headers to print. There are lots more.
Shahzad Piracha commented
That's exactly what I want as well! Right now you have to assign master pages manually to your chapter pages or opening pages and if text reflows, you're screwed and have to start all over.