This is where a dog is really, really mean to anyone and everyone, anything and everything, whether rabid, genetically tampered with, or trained from birth to be that way. If the dog has an owner, then sometimes even the owner can get on the dog's wrong side from time to time.
This type of dog is not a Hell Hound, but is a rather normal and standard dog aside from his viciousness. He CAN be kicked, but 9 times out of 10 Failure Is the Only Option where that is concerned. Indeed, kicking him successfully will often make you look reasonable.
NOT a Big Badass Wolf, though given his temperament, he may as well be.
May be an Angry Guard Dog or a Bully Bulldog, although those types usually guard homes or properties. The Vicious Dog, on the other hand, is mean regardless of his size or breed and regardless of whether he's a pet/guard dog or not.
The trope takes its name from the frequent signs on the front of homeowners' gates, usually reading simply "Beware Of Dog," that warn visitors about the potential badness of the resident pooch.
- The poodle in There's Something About Mary. Played for Laughs.
- "The Beast," the giant Mastiff dog in The Sandlot, who terrorizes the land next door to the titular sandlot where the kids play baseball, to the point that he's become something of a legend and the kids have to take great care not to knock their baseballs over the fence to where he is; getting back a Babe Ruth-signed ball drives the second half of the movie. Subverted--he turns out to be a Gentle Giant once the kids get to know him.
- The sled-dog Demon in Snow Dogs behaves this way due to a sore tooth.
- Max, the Tibetan Mastiff in the 1993 film Man's Best Friend, is this due to being genetically enhanced.
- The 1977 film The Pack is about a group of dogs that behaves this way.
- The 2006 horror movie The Breed has the protagonists being stalked by a group of dogs that embody this trope.
- Chopper, Milo Pressman's dog in Stand by Me, has this reputation. Subverted.
Jamal: I believe in free will. If my dog wishes to hate everyone in the world but myself, it is free to do so.
- Farmer Maggot's dogs Wolf, Fang and Grip in The Lord of the Rings.
- Wolvogs, the genetically engineered dogs of Oryx and Crake, will rip you to shreds without hesitation.
- WKRP in Cincinnati: As a Running Gag Les had a bandage somewhere on his person in every episode. (This stemmed from actor Richard Saunders having a cut on pilot taping day.) Eventually we learn that he has a vicious dog at home.
- Seen sometimes on Victoria Stillwell's dog-training program It's Me or the Dog.
- Shadow's dog Interceptor in Final Fantasy VI, only being obedient to Shadow himself and nice to Relm on their first meeting.
Shadow: Leave us. The dog eats strangers...
- The Runaway Dogs from EarthBound will attack anyone who stands on their way, even defenseless children. On the other hand, once you've gotten enough levels, you can boot them all you want as revenge and put them down in one shot at that.
- Oscar the dog from Kick Buttowski.
- Gru's... dog?.. thing from Despicable Me, who strikes fear in everyone, even its master. That is until Agnes comes along.
- Popular parody: Picture of a firearm. "Forget the dog, beware of the owner."
- This news report. (It's where the trope image comes from.)
- Truth in Television where dogs who are trained and bred to fight are concerned. Rottweilers in particular have gotten a bad reputation for being vicious because of this.
- Beware the dog