It could previously be obtained by pre-ordering the game from Steam, GameStop or from Game (UK), and can now only be obtained through the Game of the Year Edition of Dead Island. It is a combination of a Baseball Bat and a buzz saw.
The Ripper is useful for cutting limbs off zombies and other enemies, and can make a nice alternative to a Machete. It should be noted that the weapon's weight means that more stamina is consumed with each swing, so accuracy is important. Also worth mentioning is that when created, the durability of the weapon is decreased, meaning more repairs are necessary for it to keep its condition good. Since it retains the original weapon's stats and type, the resulting modded weapon will still be considered a blunt weapon, even though it functions as a sharp one. This means that stat bonuses for sharp weapons (such as Xian's) do not apply, but blunt weapon ones (such as Sam's) do.
A rotating Circular Blade attached to the end of a baseball bat. This is a very good medium range melee weapon and will hack and slash through enemies without any trouble. For the most part, it requires only a light amount of stamina to use.