Cheat Mode
To bring up your "Commands bar", press the [C] key. This can also be changed in your settings to any key you want. When the "Commands" bar pops up, type these codes below. This only works for single-player mode. You also have to enable cheats when creating a new world.
ascend - Moves you to the next platform above your position.
atlantis <on/off> - Toggles "Atlantis Mode".
biome - Tells you what biome you are currently in.
bring <entity> - Brings a specified entity to you.
cannon <strength> - Shoots a primed TNT block toward where you're pointing.
chest <drop/get/fill/swap> - Access commands of chests.
firedamage - Toggles player fire damage on/off.
flammable <block> [catch/spread] - Sets the specified block at a specified flammability level.
fly <speed> - Allows the player to fly at a specified speed.
freeze - Freezes mobs so they can't move or attack you.
goto <name> - Go to a waypoint.
grow - Grows all wheat and spruce trees on the map.
heal <health points> - Heals the player at a specified number of health points.
health <min/max/infinite> - Refills health to a specified level.
help <command name> - Gives more information on the specified command.
home - Teleport to the spawn point.
infiniteitems - Toggles infinite items on/off.
instantkill - Instantly kills the animal or monster you hit.
instantmine - Toggles "instant mine" on/off.
instantplant - Instantly grows what you plant.
itemdamage - Toggles breakage or usage of an item on/off.
jump - moves you from where you are to where you're pointing.
clear - Clears the console.
clearwater - Toggles the clarity of the water on/off.
clone <amount> - Clones the block being pointed at.
confuse <distance> - Confuses mobs.
cyclepainting - Cycles through the painting you are pointing at.
damage - Toggles player damage on/off.
defuse - Defuse all nearby TNT that is active.
descend - Moves you to the next platform below your position.
destroy - Destroys the current item.
difficulty <0/1/2/3> - Toggles difficulty from 0 (Peaceful), 1 (Easy), 2 (Medium), and 3 (Hard).
dropstore - Transfers everything from your inventory to a chest, which is spawned next to you.
duplicate - Duplicates and drops the current item stack you're holding.
explode - Sets off an explosion in your area.
falldamage - Toggles player fall damage on/off.
keepitems - Keeps your items after you die.
kill - Kills the current player.
killall <mob type> - Kills a specified type of mob.
killnpc <all/animal/monster> - Kills specified living things nearby.
light - Toggles permanent lighting on/off.
listwaypoints - Lists all waypoints on the map.
longerlegs - Makes your legs longer.
mobdamage - Mobs can't give you damage.
platform - Puts a glass block under your feet.
rename <command name> <newname> - Renames a command name to a new command name of your choice.
ride - Allows you to ride the living creature you are pointing at.
setspawn <x-coordinate> <y-coordinate> <z-coordinate> - Sets the spawn point to a specified coordinate.
setspeed <speed/reset> - Sets the speed in which the player moves to a specified speed/resets it.
skin <username> - Change the player skin to any Minecraft skin.
slippery <block name> - Makes the specified blocks slippery.
spawn <name/ID/random/list> <quantity> - Spawns an individual creature.
spawnportal - Spawns a portal nearby.
superheat - Turns all items into their smelted form. Ex. - Sand turns into glass.
tele <x-coordinate> <y-coordinate> <z-coordinate> - Teleport to a specified coordinate.
useportal - Automatically teleports you to the Nether. Use this command again to go back.
waterdamage - Toggles player water damage on/off.
weather <lightning/thunder/rain> - Changes the weather.
world <load/save/seed/new/exit/list/backup> - Controls your game save from the "Command" bar.
Status Effects On Player
Press [T] while in singleplayer game (also known as the 'talk' button for minecraft online), to access the speech/input for the codes:
/effect <playername> 22 <time in seconds> <lvl 1-255> - Absorption.
/effect <playername> 15 <time in seconds> <lvl 1-255> - Blindness.
/effect <playername> 12 <time in seconds> <lvl 1-255> - Fire Resistance.
/effect <playername> 3 <time in seconds> <lvl 1-255> - Haste.
/effect <playername> 21 <time in seconds> <lvl 1-255> - Health Boost.
/effect <playername> 17 <time in seconds> <lvl 1-255> - Hunger.
/effect <playername> 7 <time in seconds> <lvl 1-255> - Instant Damage.
/effect <playername> 6 <time in seconds> <lvl 1-255> - Instant Health.
/effect <playername> 14 <time in seconds> <lvl 1-255> - Invisibility.
/effect <playername> 8 <time in seconds> <lvl 1-255> - Jump Boost.
/effect <playername> 4 <time in seconds> <lvl 1-255> - Mining Fatigue.
/effect <playername> 9 <time in seconds> <lvl 1-255> - Nausea.
/effect <playername> 16 <time in seconds> <lvl 1-255> - Nightvision.
/effect <playername> 19 <time in seconds> <lvl 1-255> - Poision.
/effect <playername> 10 <time in seconds> <lvl 1-255> - Regeneration.
/effect <playername> 11 <time in seconds> <lvl 1-255> - Resistance.
/effect <playername> 23 <time in seconds> <lvl 1-255> - Saturation.
/effect <playername> 2 <time in seconds> <lvl 1-255> - Slowness.
/effect <playername> 1 <time in seconds> <lvl 1-255> - Speed.
/effect <playername> 5 <time in seconds> <lvl 1-255> - Strength.
/effect <playername> 13 <time in seconds> <lvl 1-255> - Water Breathing.
/effect <playername> 18 <time in seconds> <lvl 1-255> - Weakness.
/effect <playername> 20 <time in seconds> <lvl 1-255> - Wither.
Command Prompt Cheats
Press [T] while in singleplayer game (also known as the 'talk' button for minecraft online), to access the speech/input for the codes below.
As long as you clicked "Allow Cheats: On" when creating the world (under the "More World Options" button), these cheats will work. Switching between Survival and Creative modes can be quite useful. For example: If you switch to Creative Mode after a respawn, you can fly to the spot where you died to quickly retrieve your items. You can also switch to creative to prevent death; when you're caught in lava or water, switching to creative will make you invincible as long as you're still in that mode. Creative Mode has every item available through a selection screen, accessible in the same way as the normal inventory screen. You can use it to select an item you need, such as food or weapons, and dragging the item(s) to the "Survival Inventory" tab or the quick access bar.
Changes the game mode to Survival - /gamemode 0.
Changes the game mode to Creative - /gamemode 1.
Changes the game mode to Adventure - /gamemode 2.
Changes the game mode to Spectator - /gamemode 3.