A Medallion.
A Medallion is an item that can be used to rename tamed mobs and to tame Big Cats and Kitties. It is crafted with two Leather, a Diamond and three Gold Ingots. An alternative and much cheaper recipe can be used, which involves using two Leather, and a Gold Ingot.
When renaming a mob with a Medallion, they are not consumed upon using them, they are only used when taming a Big Cat or a Kitty.
Recipes
Template:Grid/Crafting Table