Lots of stories about dogs saving their owners from a cougar attack. Dogs get the worst of it but survive.
The Dogo Argentino is one that I'd match up pretty evenly with a cougar.
Austin Forman, left, was saved from a cougar attack by his 18-month old golden retriever, Angel.
Dogo argentino
http://www.youtube.com/watch?v=CwrAXNfcgns
http://www.cbsnews.com/2100-201_162-4996138.html