There is no answer because answerers must only state their opinion.
My opinion for small dogs:
Maltese, Chihuahua, Yorkie, Poodle, Dachshund, Pomeranian
My opinion for medium sized dogs: Bearded Collie, Border Collie, Samoyed, Siberian Husky, Whippet.
My opinion for large dogs: Afgan Hound, Alaskan Malamute, Beauceron, Belgian Sheepdog, Bernese Mountain Dog, Collie, Dalmatian
My opinion for giant dogs: Great Pyrenees, Kuvasz, Newfoundland
But these are the breeds I like, check out what kind of breeds you like at: http://www.justdogbreeds.com/dog-breeds.html
The world's rarest dog breed is the New Guinea Singing Dog.
The Most Popular Breed of Dog is the Labrador Retriever.
The Affenpinscher is the second smallest breed of Dog.
There is not a specific dog breed that is smarter than any other dog breed in the world than there is in the USA, but the smartest dog breed are poodles.
a cool breed
felicia
Sinbad, the dog that was abroad Campbell in World War II was a mixed-breed (mongrel) dog.
the great dane is the tallest dog breed while the Bullmastiff is the heaviest dog breed.
The World's Most Popular Breed of Dog is the Labrador Retriever.
The Most Popular Breed of Dog in the World is the Labrador Retriever.
The Labrador Retriever is the most popular breed of Dog in many countries the world over.
Although the current World's Tallest Dog is a Great Dane, the tallest breed of Dog is an Irish Wolfhound.