A woman I used to work with had 2 german shepherds with Schutzund (sp?) 3 certification. Her ex tried to break into her house one night. The dogs knew him very well, but when they saw she was in danger, the dogs worked together to trip the man, while one got a nice firm grip on his neck. They kept him that way until the police showed up. Don't ever underestimae a dogs ability to sense a dangerous situation. Their intuition (especially, in the working and herding groups) is beyond compare.
The next most effective thing is purely the sound of a pump shotgun. It's the sound of impending death.
