The smallest goat in the world is the Nigerian Dwarf Goat and as its name suggests, is native to West Africa. They measure between 40 and 56 centimeters tall at the shoulder and weight between 27 to 36 kilograms. These goats are easily domesticated and live on several different continents. They have good meat and produce a surprising amount of milk per day for their size; 1-3 kilograms. They have a rather grim history in North America as they were brought here as food animals for large cats in zoos.
If they are raised by hand; meaning that they were fed from infancy from a bottle by a human, they are very well socialized towards people. Some even like to come into the house although I wonder if they can be toilet trained. Neutered males make the best pets as they carry a minimal amount of scent and their horns are usually cut off in infancy to protect their owners and the herd.