Jack o' lantern
Jack-o-lanterns can be used as a square light source. It glows much brighter than a torch. If you place it in the helmet slot in your inventory you can use it as a mining cap. It will allow you to see very far even at bedrock level.
Jack 'o' Lanterns are made by placing a torch underneath a pumpkin when in the crafting interface or your inventory's or the 3x3 crafting bench.