In a zombie apocalypse, a weapon is a must-have, and while traditional weapons like baseball bats and crowbars will keep you alive for a small amount of time, the true survivors are going to be packing custom gear. "Dead Island" attempts to replicate this with custom weapons designed based on blueprints scattered around the zombie-filled island of Banoi.
These custom weapons require a blueprint to unlock, at which point you can build the weapons at any work bench, presuming you have the ingredients. These usually require a base weapon, paired with seemingly-random objects scattered throughout the world.