Mineclient
A lightweight mod that keeps the vanilla feeling, but adds some necessary tweaks and improvements
Mineclient

This mods adds some great improvements to the game, such as new commands, and some stuff to edit items data. The mod will get more features in the future, but this is the very test alpha of the mod. Or like they say in Minecraft: Here be dragons!
Here's a very funny YouTube Video About the mod, explaining how it works and entertaining at the same time!
commands usually start with two or three slashes.
List of current commands: ---
///msummon
> Usage: ///msummon <amount> <entity_id> >> Summon hundreds or even thousands of entities at once, for the ultimate lag party! >>> (requires OP [L3])
//explode
> Usage: //explode <amount> >> Creates massive explosions >>> (requires OP [L3])
///attack
> target to attack, amount of damage, name of the attack > > (requires OP [3])
///despawn
> target to despawn
>> | NOTE: You can despawn yourself, which will break the entire world (rejoin to fix) >>>(requires OP [L3])
//fire
> [add: target to put on fire, amount of burning time] [extinguish, target to distinguish] >>(requires OP [L3])
//invinc
> makes you invincible >> (requires OP [L3])
///forceitem
> item to give, amount of that item (no limit!) >>(requires OP [L3])
///modify
>(nerds only :) (requires OP [L3])
///nbt
>copy >>will copy the nbt from the item from your main hand >>>(requires OP [L3])
//msg
> player to message, should it show up in action bar? (above hotbar), your message >>NOTE: this message is anonymous. >>>This does not require any privileges.
//smite
> target - this will strike and kill annoying players >>(requires OP [L3])
//vanish
>gives you invisibility forever, type it again to become visible again! >>(requires OP [L3])
//warp
>dimension - teleport to the desired dimension! >>(requires OP [L3])
///fakeblock
> usage: ///fakeblock <blocktype> <collision?> >>Create (ghost) blocks that can be put even in the void! >>>(requires OP [L3])
single-slash commands
/gmc, /gma, /gms, /gmsp - change your gamemode. (requires OP [L3])
I probably missed some, but you can find that out! ;)