Jack o'Lantern

Jack-O-Lanterns are solid blocks implemented in the Halloween Update on October 31st 2010. It can be created by combining a pumpkin and a torch. They are intended as a purely decorative addition although they can also be used as a light source.

As with the pumpkin, a Jack-O-Lantern can be placed anywhere as long as the block directly beneath it is not air, glass, ice, glowstone or any form of fluid; thus, they can be placed at the bottom of lakes or oceans, allowing the user to easily explore underwater areas. However, it will remain in place if you remove the block below it after placing it. They emit light in every direction and the face does not need to be visible to emit light,so it can be very useful in creating hidden lights.

Jack-O-Lanterns produce the same amount of light (level 15) and share the same ability to stay lit underwater as glowstone, making them more effective and more reliable than torches.

Jack-O-Lanterns can also be used to make a Snow Golem.

Trivia

 * With the Alpha 1.2.0_02 update on November 4th 2010, all Jack-O-Lanterns on worlds were converted back into Pumpkins in name only.
 * In Beta 1.1_02, Jack-O-Lanterns are labeled Pumpkins when moused over in the inventory screen.
 * Jack-O-Lanterns had, up until Beta 1.2, the same icon and name in the inventory as pumpkins, making it impossible to tell which is which just by looking at them. However, it isn't possible to stack Jack-O-Lanterns with Pumpkins.
 * Unlike Pumpkins, Jack-O-Lanterns cannot be worn.
 * As of Beta 1.5_01, Jack-O-Lanterns that already exist in-game now all appear facing the opposite way they were placed before the update. Placing a Jack-O-Lantern will also have it placed facing away from you, as opposed to facing in your direction, as was the case before the 1.5_01 update.
 * Jack-O-Lanterns cannot be placed on Air, Fences, Glass, Ice, Pistons, any Stairs, Iron Bars or Sticky Pistons.
 * Jack-O-Lanterns will melt Snow and Ice.
 * In SMP, Jack-O-Lanterns appear green on a map.
 * When attempting to push a Jack-O-Lantern with a piston, it will break and drop as a resource.
 * If a player removes the solid block beneath a Jack-O-Lantern placed underwater, swimming directly beneath it and touching the Jack-O-Lantern will cause the game to think the player is above water, allowing the player to refill on air without surfacing.
 * This was likely the replacement for Lanterns