World's Sharpest Knife?

Is there really a world renowned knife that is considered the sharpest ever constructed? There are many blade videos and articles claiming their knives are the sharpest in the world so a great debate exists. Therefore, this post, without insulting anyone's claims, is sharing some of these opinions rather than narrowing down to one knife and one knife only.

Is it the type of metal or just any metal sharpened to its thinnest edge considered the sharpest?

Your comments are greatly appreciated and welcome.

Image: Rockstead Knife