2. Cavalier King Charles Spaniel - The Cavalier King Charles Spaniel is a smaller, affectionate breed of British origin. It is the 18th-most popular dog breed of 196, according to the AKC. The King Charles Spaniel is gentle in nature due to its kind, easy-going, yet playful temperament and is great around children, babies, and small pets. Thanks to its tiny stature under 13 inches in height, it is classified as a toy breed.