Sometimes referred to as "Hobo Coins" these are genuine cents that have been hand carved to show a new design. They are a form of art and are not mint errors, but are collected as art and history items.
Some people have wondered if altering a US coin is illegal. As long as there is no intent to defraud someone, as in counterfeiting, it is not illegal.
The following photos are courtesy of Joeys Carved Art.