Now I've been playing minecraft since it came out made some great memories and had some good times, but everything changed when i first played Herobrines mansion by Hypixel. I couldn't believe that it wasn't modded in some way. So I started to research and found out that there are more commands out there than just /gamemode or /weather, and these commands changed my minecraft experience entirely. Here are some of the most basic player commands that I find myself using very frequently and are very usefull when it comes to adventure map making.

Note: pressing TAB while inputing commands will cycle through them. So feel free to experiment on them.
Also the easiest way to get command blocks is just a /give <player> 137 or minecraft:command_block


/gamerule keepInventory true/false    This will make your items and armor stay with you on death
                mobGriefing true/false      This will disable the block breaking effect for creepers, endermen, ghasts, ect... but they                                                          will still do and give damage to players
               doDaylightCycle true/false   Sun or moon will stay where they are changed only by /time set commands
               doFireTick true/false          Stops the spreading of fire
               doMobSpawning true/false  Mobs wont spawn unless there are spawners, spawn eggs, or command blocks

/effect <player> <effect> <seconds> <amplifier>  
            Sereck       1            10             3                                  So this would be speedboost 3 for 10 seconds


Effect number list (Add this to the <effect> section)

1 - Speed (minecraft:speed)
2 - Slowness (minecraft:slowness)
3 - Haste (minecraft:haste)
4 - Mining Fatigue (minecraft:mining_fatigue)
5 - Strength (minecraft:strength)
6 - Instant Health (minecraft:instant_health)
7 - Instant Damage (minecraft:instant_damage)
8 - Jump Boost (minecraft:jump_boost)
9 - Nausea (minecraft:nausea)
10 - Regeneration (minecraft:regeneration)
11 - Resistance (minecraft:resistance)
12 - Fire Resistance (minecraft:fire_resistance)
13 - Water Breathing (minecraft:water_breathing)
14 - Invisibility (minecraft:invisibility)
15 - Blindness (minecraft:blindness)
16 - Night Vision (minecraft:night_vision)
17 - Hunger (minecraft:hunger)
18 - Weakness (minecraft:weakness)
19 - Poison (minecraft:poison)
20 - Wither (minecraft:wither)
21 - Health Boost (minecraft:health_boost)
22 - Absorption (minecraft:absorption)
23 - Saturation (minecraft:saturation)

/give <player> minecraft:<Item> <quantity> <damage> {ench:[{id:1,lvl:1}],display:{Name:"Name goes here",Lore:["Lore goes here"]}}

Enchantment Ids
0 | minecraft:protection | Protection
1 | minecraft:fire_protection | Fire Protection
2 | minecraft:feather_falling | Feather Falling
3 | minecraft:blast_protection | Blast Protection
4 | minecraft:projectile_protection | Projectile Protection
5 | minecraft:respiration | Respiration
6 | minecraft:aqua_affinity | Aqua Affinity
7 | minecraft:thorns | Thorns
8 | minecraft:depth_strider | Depth Strider (1.8)

34 | minecraft:unbreaking | Unbreaking

Weapons

16 | minecraft:sharpness | Sharpness
17 | minecraft:smite | Smite
18 | minecraft:bane_of_arthropods | Bane Of Arthropods
19 | minecraft:knockback | Knockback
20 | minecraft:fire_aspect | Fire Aspect
21 | minecraft:looting | Looting

34 | minecraft:unbreaking | Unbreaking

Tools

32 | minecraft:efficiency | Efficiency
33 | minecraft:silk_touch | Silk Touch
34 | minecraft:unbreaking | Unbreaking
35 | minecraft:fortune | Fortune

Bows

48 | minecraft:power | Power
49 | minecraft:punch | Punch
50 | minecraft:flame | Flame
51 | minecraft:infinity | Infinity

Fishing Rods

61 | minecraft:luck_of_the_sea | Luck of the Sea (1.8)
62 | minecraft:lure | Lure (1.8)
 
The /summon command has quite a few uses and fun things to mess around with.
/summon <Entity> (make sure its capital) [x] [y] [z] cordinates of the summon. For example /summon Skeleton 123 456 789
 Note: The ~ symbol means reletive to the command block or player giving the command. They go into the x y and z spots.
Example: /summon Zombie ~ ~5 ~   With the reletive symbol this means that it will summon the zombie 5 blocks above the player.

It is also possible to summon mobs with equipment by adding a data tag.
/summon Skeleton ~ ~ ~ {Equipment:[{id:293}]}  This will summon a skeleton with a diamond hoe.
Here are a few more summon commands that use certain entities like falling sand. Feel free to have fun with these.

/summon EnderCrystal ~ ~10 ~
/summon FallingSand ~ ~3 ~ {Time:1,TileID:52,TileEntityData:{EntityId: Creeper}}
/summon Slime ~ ~ ~ {Size:100}
/summon Fireball ~ ~3 ~ {ExplosionPower:50,direction:[1.0,0.0,0.­0]}
/summon Cow ~ ~ ~ {Riding:{id:"Giant"}}
/summon Cow ~0 ~0 ~0 {Invulnerable:1}
/summon Zombie ~ ~ ~ { Equipment:[{id:245 }, {id:267}]}
/summon Cow ~ ~ ~ {Riding:{id:"Cow", Riding:{id:"Cow", Riding:{id:"Cow"}}}}

How do you summon a charged Creeper?
/summon Creeper ~ ~ ~ {powered:1}

Tellraw commands and basicly like a /tell command but you can change alot withing your text. Your text goes in the quotations and then put true after each effect that you want onto your text.

/tellraw @a {text:"Hello there",bold:true,underlined:true,strikethrough:true,obfuscated:true}

It is also possible in 1.8 or higher to use command blocks to make signs that run commands when you use them, instead of downloading some plugin to do the same.
/setblock ~ ~3 ~ minecraft:wall_sign 2 replace {Text1:"{text:\"This is Line 1\"}",
Text2:"{text:\"This is Line 2\",color:dark_red,clickEvent:{action:run_command,value:\"/say This command is activated as the player\"}}",
Text3:"{text:\"This is Line 3\",color:dark_blue,clickEvent:{action:run_command,value:\"/effect @p 1 10 10\"}}"}

/kill @e[type=Creeper,r=20]     @e targeting entity  in a r= radis of 20 blocks

/summon EntityHorse ~ ~ ~ {Type:4,Tame:1}
/summon Creeper ~ ~ ~ {ExplosionRadius:100,Fuse:30,Riding:{id:Spider}}

When arranging your own commands and experimenting with them the most frusterating part can be getting the parentheses []{} in the right places. They need to be balenced on both sides.

There will be more to come, I will try to update this pretty often. You can find a Wiki on almost all of this if you would understand that better.