Java Edition mentioned features

No mods!

Partially implemented
These features had been shown by a Mojang staff member, but either had no further development or were canceled shortly after.

Dirt slab


Before stone slabs were added to 0.26, Notch ran a test of dirt slabs. In the test they replaced dirt blocks, so that dirt surface without grass was half a block lower than grass. However it made a mess of the sides of cliffs and underground. They were never added to the actual game and were only mentioned once. They replaced all dirt blocks and did not grow grass on top.

Dyed planks


Dinnerbone asked Twitter how they would feel about colored planks. He announced the results as being, "30% 'please no', 80% 'yes please'. Yes, that's 110%. I don't even know." Despite this, he canceled the idea and instead added hardened clay, which can be dyed. The dyed planks were abandoned after Dinnerbone realized they would require slabs and stairs of each color too. However, each tree type has their own color plank. This includes stairs, slabs, doors, fences and fence gates. However, they are not dyed, just simply the color of the appropriate tree.

Lantern
Lanterns were crafted blocks originally planned to be added in the Halloween Update. However, they were delayed due to lack of time and were going to be implemented in a future update.

With the addition of the lantern, torches would flicker out and need to be re-lit with flint and steel. The lantern would serve as a permanent source of light. According to Notch, when the update would occur, all torches placed on the map, in the inventory, and in chests prior to the update would be converted to lanterns. To do this, the lanterns would use the (former) block ID of torches along with a re-skin.

On January 13, 2011 Notch claimed that lanterns were "postponed", and added on January 20 that he was "not sure" when they would be implemented. Notch announced on November 18, 2011, at the Mojang Panel at MineCon 2011, that lanterns would not be added to Minecraft due to large negative community response towards the effects the new item would have had on torches. Instead, other types of lighting would be added, such as redstone lamps and glowstone.

Lectern
The Lectern was an old project of Dinnerbone's. It was meant to be a stand for books so you could easily read them. He was well on his way to creating it when he encountered problems and scrapped the idea, but mentioned that he might pick up work on the lectern in the near future. Dinnerbone stated in his Reddit AMA on December 18, 2013 that he had revisited lecterns but scrapped them again as "something about them just didn't feel right".

Sky Dimension
The Sky Dimension was a planned dimension in Minecraft, intended to be the opposite of the Nether. It was ultimately replaced by the End.

Fish
Fish were a passive mob that Notch showed interest in adding. In the Halloween Update, Notch said he would add fish. However, they were only added as an item. There is no coding for a fish mob in the game itself, nor is there a model that currently exists. Despite being two years since the mob was first mentioned, Jon Kagstrom has stated that he is planning to add fish as a mob. Notch states in the reference the 'ability to catch fish' which is already implemented. Nothing says anything about adding a model. During [ Notch's AMA] on Reddit, when asked about what happened to his plans of adding fish as a mob, he responded, "Oh yeah, the fish!"

Mentioned
These features were mentioned at one point but later abandoned or their current status is unknown. Note that some of these features were mentioned by developers who either no longer work at Mojang, or no longer work on Minecraft.

Audio loops
Audio loops have not yet been added to the game, but may be implemented to play when the player is in a specific location (In caves, forests, oceans, and beside a waterfall). This has been partially added in 1.4 with the addition of lava and water ambient sounds.

Friends list
Notch mentioned on his blog, The Word of Notch, that friends lists would be added after Beta 1.8. The Minecraft documentary team of 2 Player Productions filmed a Keynote roadmap, containing these lines. Kristoffer mentioned on Twitter that he is currently working on friends lists for Scrolls, then for other Mojang games. These will be available for players with Mojang accounts. At MineCon 2012 Jeb stated that it would be a large implementation on the server side and will be used for all Mojang games, and that is a big project.

Lua scripting
Lua Scripting was a feature mentioned by Notch as a way to create server side modifications.

Players will not have to download scripts within or outside of the client, and therefore no client-side modifications will be necessary.

The server would be able to create custom commands, assign certain server functions to blocks, and create user groups.

Notch has said that he wanted Lua to be an extension for Minecraft. He does not want Lua to turn Minecraft into a game engine. Essentially, Lua, although a nice addition, will not revolutionize game-play in Minecraft.

Resource packs
Erik Broes mentioned that there may be easier customization of chat and sheep colors

Ryan Holtz stated that he wanted to improve the rendering system to allow for customizable models and animations. Dinnerbone later stated that player models would not be able to be changed.

Panda
Dinnerbone once tweeted about pandas in response to the question "If you could code any mob into the game, what would it be?"

On December 18, 2013, on Reddit, Dinnerbone answered the question "If you could add one feature to Minecraft without the hassle of coding or modeling, just anything, and you wouldn't need anyone's permission: What do?".

Red dragon
Notch revealed during the 8th Seecret Friday Update that he would add dragons, one being the ender dragon, the other being red dragons. Jeb informed participants of his AMA on Reddit that he would add red dragons, but was unsure exactly how. The red dragon has not subsequently been added.

On October 22, 2013, Dinnerbone tweeted that the red dragon is "shelved" and not in development.

Later, on December 15, 2013, Dinnerbone wrote on Reddit that there will be red dragons in Minecraft one day.

Seasons
Dinnerbone mentioned on Twitter that he was experimenting with adding seasons, and varying the length of day and night according to season. He also mentioned it during MineCon 2013. Seasons may include changes in color of tree leaves and may also be tied to real time.

Spike block
Spike blocks were originally planned for, working by extending and retracting spikes (and making them more "spike pistons" than anything), but were replaced by sticky pistons. On May 28, 2012, Dinnerbone stated that he'd like to add spike blocks, but is unsure of how to implement them.

Workbench (Plugin API)
The Plugin API, dubbed "Workbench", is a feature that allows mod developers to easily add more content to the game. In contrast to mods, plugins will not require any alteration of the minecraft.jar file itself, although they will also be slightly limited in their feature set. The Bukkit team will help make the official Plugin API.

Inventory changes
An inventory rewrite was originally added in the snapshot 14w17a for 1.8, but a roadblock was hit and they had to shelve it before the release of 1.8. Other changes to the inventory have been mentioned, including spectators can now look at people's inventory, visible health/armor bar on all players,, seeing players' GUI when spectating from their POV and the return of shift-double-clicking

Brief mentions
These features were briefly mentioned, but no further information was given after that.

General features

 * More animals such as fish, birds, and tree animals, to make the game seem more alive.
 * More sea life (This has partly implemented in 14w25a with the addition of guardians)
 * More structures in biomes
 * More dimensions
 * More rare structures and terrain changes
 * More ores and cave types
 * Height-based content, something like vertical biomes.
 * All exclusive Pocket Edition features ported to PC

More specific features

 * Ocean Ambience
 * Coral. Notch abandoned the idea, stating "It's really hard to draw a single block that looks like corals, since it's really more about crazy amounts of variation and diversity. But I do know that the corals will have tiny fish particles around them."
 * The ability to choose what work saves to the level files
 * Storing of achievements and statistics online
 * Animated swinging doors
 * Better construction analysis
 * Cherry trees
 * Colliding clouds
 * Vertical redstone
 * Ability to design village buildings
 * Minecart with dispenser;, image may have just be showcasing the custom tile displays in minecarts which was added in the next snapshot, 13w02a.
 * Easier way to implement terrain changes
 * In early Alpha, Notch mentioned two more gamemodes, Team Survival Mode and Fortress Mode
 * Mesa temple
 * Books editable anywhere, not just at the end of the page
 * Silk touch yielding double half slabs
 * Custom tabs and preset inventory layouts for the Creative inventory
 * Ability to pause the game in multiplayer, but only for ops. Users will then get to chat until the game is back.
 * Copy and paste support on signs
 * Minecarts usable as boats
 * Fallen trees (like what is currently in Pocket Edition)
 * A new male mob that has no clothes. Not currently being worked on.
 * Flower pots breaking when hit by arrows.
 * Turtles
 * Utilising the space above the Nether ceiling for something else.
 * Enchanted items apply attributes on use.
 * A Capture the Flag gamemode
 * Adding more places to display scoreboard scores.
 * Colored lighting
 * A better UI for server admins/ops, inspired by the twitch user moderation menu.
 * A resource pack-related feature that allows improved russian font display
 * A new system that could alter weapon behavior.
 * This has been partially implemented in 15w34a, with the implementation of attack speed
 * A hug animation
 * Improved camera controls
 * A gamerule which prevents rain/snow
 * This has been slightly implemented in 16w38a, with the implementation of the gamerule doWeatherCycle, which disables the weather from changing.
 * Rewrite the liquid and lighting engine
 * Changes to the world format - storing which version the world was last opened in, modularized and stored in 16 block high sections, ids per chunk
 * Rewriting the key bind system.
 * Building a custom sound system.
 * Multithreaded terrain generation rendering.
 * A more user-friendly launcher.
 * Fixes to chunk loading.
 * Using the killer rabbit killing mobs for something.
 * A marker entity.
 * Better autocomplete (prompt whilst writing) and auto GUI creation for commands.
 * Reindeer - initially suggested for Christmas 2015.
 * OAuth
 * Nether portals placing players in front if possible.
 * The ability to remove enchantments from an item.
 * Scarecrows
 * More colors and texture pack customizations of maps
 * Cave maps - Notch stated that they are "an interesting idea".
 * Uncarved pumpkins.
 * Custom paintings
 * Rainbow crystalline caves
 * Server portals
 * Fireworks having effects on mobs, such as scaring wolves.
 * Dinnerbone has stated he has an "Ultimate Plan" with endermites that might include the dragon egg.
 * Corn
 * In game lore
 * "Crazy ideas on world generation algorithms"
 * Another rabbit skin
 * Making parent rabbit color influence child color
 * JSON support on signs and possibly implementing a way to "make it work in survival" . Searge later said "The plan is to eventually have every text that can be displayed on the screen use the text component system, then using § won't be necessary anymore."
 * Being able to make the world border's center slowly move
 * Sheep showing their color when shorn, like the Pocket Edition
 * Dinnerbone's original demonstration of the  format for resource packs contained a sample properties file for fonts to determine character size and spacing. Despite the game code containing the code to read the files, it never actually uses them leaving character width and spacing to be determined dynamically.
 * Different types of trapdoors
 * A GUI for command blocks
 * Portable light (e.g. holding a torch in your hand which provides light).
 * A mob which camouflages with its environment - when developing the Shulker mob, Jeb initially had it so that the mob would camouflage with the surroundings, but due to difficulties with the code and rendering, he decided to abandon this element of the mob, but stated that it may happen in the future.
 * Notch once planned to make floating masses of land that required obsidian veins to stay afloat. He later stated that he disliked the idea.
 * Entities possibly being able to switch between weapons - "There are no plans right now for entities to use that [offhand] slot, but it might be a potential change in the future. It's just cleaner to have generic support for the off-hand slot than adding a special-case the player class only."
 * Minecart improvements after/in 1.10
 * Phasing out the minecart with furnace.
 * Allowing mobs to have additional random skins, similarly to horses, cats and rabbits.
 * Giving the ability to rotate and mirror structures.
 * Making it so shields are used to block attacks from the side the shield is held on.
 * New musician villager that trades note blocks, jukeboxes, and music discs.
 * Removal of the limit on the maximum number of block ids.
 * Recipes for seamless slabs and bark blocks.
 * Basalt

Joke features


Notch and other Mojang AB employees have frequently joked about adding various features to the game.


 * Searge jokingly stated that due to the fact that people didn't dislike the changes in the 15w42a snapshot, he would add a fuel requirement to crafting tables.
 * Koalas in tanks riding on planes with laser rifles was jokingly added to the "maybe later" list by Searge.
 * Hot dogs.
 * Herobrine. In every new Minecraft update like Halloween Update, Adventure Update, Pretty Scary Update, Redstone Update, Horse Update, The Update That Changed The World, The Bountiful Update, The Combat Update and The Frostburn Update it says "removed Herobrine", but Herobrine was never implemented. This has also appeared in the changelog for Scrolls version 0.103.0.
 * When Hardcore mode was announced, a joke screenshot of "Ultra Hardcore Mode" was shown, where death would revoke an account's premium status.
 * Jeb joked about adding chips if 100% of the community agreed on what type the chips would be.
 * Marc joked about adding Top Hats for 1.4.
 * A snapshot named 12marc40awesome containing various joke features such as volcanoes, more dragons, coral, fish, and fish blocks.
 * Pine cones.
 * Dinnerbone joked about adding dwarves when asked about it.
 * SethBling mentioned a downside of the command blocks on one of his livestreams, and Dinnerbone joked about removing command blocks to accommodate him.
 * Dinnerbone joked that Minecraft pizza would be a good idea to add, and as a joke KrisJelbring states pizza is confirmed to be added.
 * Mojang has made several joke features during april fools.
 * In 2011, the locked chest or "Steve Co. Supply Crate" was temporarily added which "allowed" various micro-transactions in the game.
 * In 2013, Mojang released Minecraft 2.0 which contained features such as pink withers and redstone bugs.
 * In 2014, the default sounds were and everyone's skin were replaced with villagers, which was all blamed on the villagers
 * In 2015, Mojang released 15w14a, which made all the mobs in the game friendly and lovey.
 * In 2016, Mojang released 1.RV-Pre1, which added trendy items of 2016.