Golden Apple

Golden Apples are the most difficult to obtain, but most beneficial Food item. They are extremely rarely found in dungeon and abandoned mine shaft chests, though they can also be obtained by crafting a red apple and eight gold blocks together. Eating one heals, and grants enhanced regeneration for 30 seconds, regardless of hunger level.

Advantages

 * Golden apples are the only food that can completely refill the player's health, without a full hunger bar.
 * They are also the only food items that cause temporary constant health regeneration that is not dependent on the player's hunger. This is indicated by the line of hearts bobbing up and down in a wave pattern, with each full wave restoring half a heart.

Disadvantages

 * Red apples can only be found in Strongholds or by killing Notch in SMP.
 * Golden apples have an extremely slim chance of appearing in dungeon chests. 1/125 (0.8%).
 * Since each golden apple requires 8 gold blocks, or 72 ingots to craft, they are neither time nor resource efficient to craft as the equivalent amount of gold could yield 3 full sets of Gold Armor, 18 clocks or 72 powered rails, excluding other ingredients.
 * As of the 1.9 pre-releases, health regeneration is not unique to the Golden Apple anymore and can be obtained with far greater ease by brewing a potion with a Ghast Tear.

Pre-Release
As of Minecraft's 1.9 pre-release 2, Golden Apples now have a purple-ish glow when viewed from the player's inventory. Note: The glow effect is not shown when the apple is in the player's hotkey bar, but rather only when they are viewing their inventory, a chest or furnace.

Trivia

 * Just like most other items, Golden Apples can be acquired repeatedly while in creative mode. However, the player takes no damage and does not suffer from hunger while in creative mode, making the need to eat Golden Apples or any other food unnecessary.