Smelt any of the tools to get one of the metal that was used to make it (so Iron shovel/sword/pickaxe/hoe/axe smelted = 1 iron ingot).
I would like for there to be a way to make ink sacs (i know they have no real use, but anyways) How about either: Smelting saddles, Crafting coal Crafting Melon seeds (they are black, so this kinda made sense in my head, even if its a bit crazy)
How about smelting Diamond to get A LOT of Coal? Would be kind of useless at first, but when you're stuck in a giant dark cave, anything helps.