Minecraft wiki entry for Defense, associated text: Though it is best on faction servers, cannons loaded with TNT, potions, or arrows are very fun to use and can do a lot of damage. Keep in mind that TNT will damage terrain, and that an incorrectly-built TNT cannon may blow up your house. There are many designs of TNT cannons you can use. Plus, with slime blocks, you can make them cheaper than ever.[verify]