Ender shield.

This shield would have a similar defense to a regular shield however it would have the ability to teleport the holder (when pressing the use button for the shield) but only in the event you are attacked. Much like the endermans ability at avoiding projectiles. It would be crafted with ender eyes around a regular shield, if holding the shield however in rain then you can expect to be teleported about in a random direction every minute or so. The shield could use one durability for every teleport. Upon breakage an endermite could spawn.