Life with Dogs had a post about an amazing story of a lost pit bull defending a woman and her child (whom the dog did not know previously!) from an attacker with a knife. Once the attacker had fled the scene, the woman got in her car with her child to ride off, but the dog jumped in the backseat to wait with them for police to come! Not too shabby.
On the subject of heroic pit bulls:
In March 2007 a pit bull in the Philippines gave his life to save two women from a deadly cobra.
Here’s the story of another pit bull coming to the rescue in 2009, defending a woman in a domestic disturbance:
And here’s another video of another heroic pit bull.
Defying the stereotypes. Nice.