A detailed explanation of the items from default configuration (you can add as many as you want)
The emerald armor gives you some extra hearts and a good protection (better than diamond). It doesn't have a big durability though.
The obsidian armor is not as good as a diamond armor but has a ludicrous durability.
Orax, ruby, onyx and amethyst ores support fortune and silktouch enchantments.
A caveblock is a block which allows you to see through the other blocks (like a kind of xray), players LOVE it in faction servers.
A nice crown to look like a king which gives you armor protection and armor toughness.
The anubis head gives you nightvision and some protection.
A nice witch hat which gives you armor protection and armor toughness.
The incredible legendary pharaoh head, which gives you some armor protection and armor toughness.
A cog is an item that can be used to repair an item. You just have to take it in your hand and click on a repairable item using it inside your inventory.
A incredibly powerful storm sword which allows you to strike lightning.
This magical wand has a great animation and looks really cool, you can use it to make an Energy Blast to attack entities.
Like the magical wand, the withooker has a great animation and looks really cool but it currently doesn't have any mechanic so it's up to you to decide what you want to do with it.
The dagger is a really nice weapon that can be used like a sword. By default you can use it faster than a sword.
Energy crystal sword
The energy crystal sword is an incredibly looking sword, optimized for PvP and partially transparent.
You can use the blood sword to steal hearts from your enemies.
The katana is another nice looking sword that you can customize.
Like the dagger, the Octavia sword is small and nice looking.
As powerful as an iron sword ...but so much durable! The obsidian sword is really useful.
The glass sword is a pretty powerful sword but with a low durability.
Axe of experience
You can use the axe of experience to convert your experience into bottles of experience (you'll have to lose a few percentage of experience though).
You can use the bedrock pickaxe to break bedrock and go at the top of the nether for example.
This tool allows you to harvest: it will automatically recolt and replant wheat!
The obsidian pickaxe can be used to break a lot of blocks but is similar to an iron pickaxe.
Hammers are very special pickaxes capable of mining several blocks at the same time. Legend says that they were invented by Notch but he didn't have time to add them so he only drew them into the anvil repair interface.
The most basic hammer you can find is the Emerald Hammer, it mines a square of 3 blocks per 3 blocks, this is cool in order to start but definitively not the best you can get.
Unlike the Emerald Hammer, the Amethyst Hammer mines a square of 3 blocks per 3 blocks too but with a depth of two blocks.
Take the Amethyst Hammer, improve it and you've got the Onyx Hammer. It can break more blocks than the Amethyst Hammer because it has a big durability.
Compared to his brothers, the Orax Hammer is a god like hammer : it can mine a really big square with a depth of two blocks.
The Fire Hammer mines like a basic hammer (3 blocks per 3 blocks, depth of 1) but it actually melts ores instantly! If you mine iron ore for example you'll immediatly get rewarded with iron ingots ...and it stacks with fortune!