Pig Manure - Poopin' Pigs!
Makes adult pigs poop out Manure, which can be used like Bone Meal in the world, can be used as brown dye in recipes, and can be smelted into bricks (same experience as smelting a clay ball). This gives the player a tangible reason to farm pigs instead of cows, chickens, or sheep.
Baby pigs do not poop. Obviously, baby pigs poop in real life, this is just to keep the balance on par with similar things.
Credit for the idea goes to skidznet.