You know what I wish would be added to Minecraft? Rope, which would be easily crafted using string. In multiplayer, this could be useful if you end up falling down below where getting out isn't easy. Sure, there are ladders, but I'd think it would be easier to craft rope. I was in a situation recently where I fell down recently in singleplayer, and thankfully I had enough wood with me to build a ladder as it was quite deep, but there are situations where rope would just be more useful.