Minecarts

Why not add a customisable minecart to Minecraft? You could attach items to it for a specific purpose, such as a crossbow (to make a sort of defensive turret), a lantern (to light up the surrounding area) or a fishing rod (to pull the minecart as if it had a grappling hook). Items other than those shown in the examples could also be used to give a minecart a second purpose.