This is a list of people famous enough to be known unambiguously by one of the following:
A one word nickname (Shaq)
A one word first name (Madonna)
Their only known name (Aristotle)
A one word stage name or pseudonym (Houdini)
A one word pen name (Voltaire)
The reason for such distinctions is that countless artists, composers, philosophers, politicians, writers, scientists and sports figures are known for their last name (e.g. Mozart, Shakespeare, Hitler, etc.). It is quite common and regular for last names to be used to identify historic and pop culture figures. It is another thing all together to be known uniquely within the criteria listed above.