Jack o'Lantern

A jack o'lantern is a solid block that provides light.

Crafting
A jack o'lantern can be crafted by placing a torch inside a pumpkin.

Usage
Like a pumpkin, a jack o'lantern can only be placed on top of a solid opaque block, but the block underneath can then be removed without causing the jack o'lantern to turn into an item. A jack o'lantern cannot be placed on a transparent block.

Jack o'lanterns have a direction: one side looks like a lit carved face. When a jack o'lantern is placed, the face will be facing the player.

A jack o'lantern produces a light level of 15. Despite the appearance that the light is coming out of the face side, the light is directionless and affects all blocks around the jack o'lantern equally.

A jack o'lantern cannot be pushed by a piston — it will simply turn into an item when pushed.

Creating golems
A jack o'lantern can be used to create an iron golem or a snow golem, but golems created with jack o'lanterns have the same heads as those created with pumpkins.

Tips
Jack o'lanterns have a higher light level than torches (15 as opposed to 14). Because it is a block, players can replace wall or floor/ground blocks with them for aesthetically pleasing and versatile embedded light sources, which can be especially attractive for lit paths. Jack o'lanterns can be used for a slime farm to light up the room, as they are opaque blocks which mobs can spawn on.

Jack o'lanterns share many properties with sea lanterns, glowstone and beacons, with a luminance of 15 and the ability to provide light while submerged under water. Of the three, jack o'lanterns are arguably the easiest to acquire, as their constituent ingredients can be grown (pumpkins and wood) or easily collected in the Overworld (coal and wood). Like all non-sunlight light sources, they will cause nearby snow and ice to melt.

Their ability to be submerged in water allows docks or harbors to be lit from underwater for a pleasing and functional effect that is useful to players in boats that need to see where to stop. They can also be used during underwater exploration, such as in lakes and oceans, to make underwater navigation significantly easier. Jack o'lanterns can be used as light sources for growing crops at night, and can be placed under irrigation paths to provide an aesthetic ambient glow for crops.

Jack o'lanterns are useful as trails in the Nether, as unlike torches, they will stay in place even if the netherrack beneath it has been destroyed; and unless it is directly hit, it can often resist Ghast bombs, unlike glowstone. It also stands out more than glowstone, because it cannot be found naturally in The Nether

Trivia

 * On Halloween (October 31), all undead mobs (zombies, zombie villagers, zombie pigmen, skeletons, spider jockies and wither skeletons) have a chance of spawning with either a jack o'lantern or an ordinary pumpkin equipped as headgear. The worn jack o'lanterns do not glow or emit light. Despite the Halloween easter-egg, the player cannot wear a jack o'lantern like they can a pumpkin.
 * In SMP, a jack o'lantern appears green on a map.