The most common breed of dogs are Labradors. They are highly intelligent, very active, easy to train and they make a great family pet. I would recommend buying one!
It would be the Angus breed.
The Holstein breed.
Angus cattle are the most common.
Merinos
There are no 'breeds' of chinchilla, but the most common colour is a standard grey
I know the American Shorthair is a pretty common cat, but it might not be the MOST common. :)
mutt breed cats are most common but after that is the tabby cat
Adelie and Emperor penguins are the most common to breed on the Antarctic continent.
Broad-Breasted White turkey is the most common.
i am obese too.
The Holstein.
rednose pitbull is the most commonly bred pitbull.