I thought I'd post this recent story, as it shows the importance of service dogs.
An intruder broke into this blind woman's home, assaulted her by choking her and subsequently throwing her down the stairs, but her guide dog saved her life by using a special device to call 911. When the dog did so, the intruder fled. It is uncertain whether the intruder knew the woman, or not, but her dog is definitely a hero.
This is a great example of a hero dog.
I thought I'd add some other amazing stories of hero/rescue dogs here. One of my recent commenters inspired this post, in discussing what it means for a dog to be a real hero/rescue dog. Here are real hero dogs that have heroically rescued their owners.