British Plug

The British polwer plug, also known as the type g plug is used in over 50 nations around the world from Saudi Arabia to various nations in Africa and even on Hong Kong island. It can handle a current as big as 15 amps but usually has a fuse that blows when the current at 13 amps. 

Image taken from my camera in my home

The ground pin at the top of the plug has 4 uses. It works as a key and opens spring loaded shutters for the live terminals as the plug is pushed in. It also turns on the circuit breaker if a strong current flows through it and that prevents electrical fires caused by a short circuit by turning off the whole loop.  It also safely carries an overloaded current back to the main transformer of the building preventing electic shock from a faulty appliance. If that fails the fuse will blow instead. The pin at the top of the plug also creates friction that makes the plug less likely to slide out of the socket unintentionally.