Equivalent Exchange is in a lot of mods, but if you don't know what it is, it is an exchanger that is equivalent... (example: trade a certain amount of iron for a diamond) You can craft an EE, and then put it in a crafting table to make a Charged Equivalent Exchanger. If you use a CEE, it will turn back into an EE. You can craft from the lowest mob drops all the way up to ender pearls, blaze rods, ghast tears, and so on. You can do the same with vanilla materials.