Popadopoulos must come high on the list.
The most common surname in Greece is Papadopoulos.
The most common South American surname in Argentina is Fernandez. In Brazil, the most common surname is Silva. In Chile, the most common surname is Gonzalez.
Garcia is the most common surname in Spain.
Garcia is the most common Spanish surname.
Lithuania has different top ranked surnames for men and women. The most common male surname is Kazlauskas. The most common female surname is KazlauskienÄ—.
White
I think the most common lebanese surname would either be Khouri, Elkhouri or Georgeos
The most common surname in Newfoundland, Canada is Smith.
The most common ones are Kim, Lee, and Park in that order.
Smith is the most common surname
greece's most common export is olive oil
According to The British Surnames Website, the third most common surname is "Harris". (see related link)