Do you mean real ones, or 'actors' like Lassie and Rin Tin Tin? There's the legendary Gelert, and of course Greyfriars Bobby. I'm sure I'll be able to think of more!
And of course (how could I forget, being a Poodle owner!) there was Boye, Prince Rupert's Poodle, who died at the Battle of Marston Moor.
I can remember TWO The first is Boatswain, a Newfoundland who belonged to Lord Byron. Boatswain is buried at Newstead Abbey and on his tomb you can read the poem Lord Byron wrote called "Epitaph for a dog". I've seen it several times as my family used to live not far from Newstead Abbey. You can read more if you go to: http://en.wikipedia.org/wiki/Epitaph_to_a_dog The other one is Mancs, a German Shepherd who's one of the 11 bravest dogs in history. He and his owner come from Miskolc which the nearest large city to where I live. He was part of The Spider Special Rescue Team who travelled all over the world locate earthquake victims. There's a statue of him in Miskolc. If you want to know go to: http://en.wikipedia.org/wiki/Mancs_(dog)
Hachiko, (Akita ) During his owner's life, Hachikō greeted him at the end of each day at the nearby Shibuya Station. The pair continued their daily routine until May 1925, when Professor Ueno did not return. The professor had suffered a cerebral haemorrhage and died, never returning to the train station where Hachikō was waiting. Each day for the next nine years Hachikō awaited Ueno's return, precisely when the train was due at the station. Hachikō's body is stuffed and mounted and kept at the National Science Museum of Japan in Ueno, Tokyo. In April 1934, a bronze statue in his likeness was erected at Shibuya Station http://en.wikipedia.org/wiki/Hachikō…………………………………………… Strongheart (GSD(was the screen name of Etzel von Oeringen (October 1, 1917–June 24, 1929), became one of the earliest canine film stars. After being trained in Germany as a police dog, he was brought to the United States by husband and wife filmmakers Laurence Trimble and Jane Murfin, He appeared in several movies, In the movie The Love Master (1924), Strongheart was cast opposite of Lady Jule, a beautiful German shepherd. They produced many litters, including offspring who would sire pups who grew up to be movie stars themselves. Lady Jule and Strongheart´s line survives today. http://en.wikipedia.org/wiki/Strongheart………. Buddy (GSD) became the forerunner of guide dogs for the blind in the US. and was hailed as a national heroine. Love Leads the Way (film ) is based on the true story of Morris Frank and his fight for seeing-eye dog legislation in America. http://en.wikipedia.org/wiki/Morris_Frank