Single Player Commands

Single Player Commands for Minecraft 1.6.2/1.6.1/1.5.2 is a modification that adds support for in-game commands to modify your world.
Manual Installation for Minecraft 1.6.2 and newer:

1.Close Minecraft launcher (if open)
2.Navigate to where minecraft is installed (eg: on Windows %appdata%/.minecraft)
3.Go to versions and copy the 1.6.2 directory and name it something else (eg: 1.6.2.mods). Alternatively, if you 4.have done this for another mod already backup the Minecraft JAR.
5.Open the jar file (using an archive utility, such as 7zip) in the mod directory you created (eg: 1.6.2.jar) and copy all of the files into it except for WorldEdit.jar
6.Delete the files in the META-INF directory except for MANIFEST.MF
7.Close the jar file
8.Copy WorldEdit.jar into .minecraft/bin
9.Rename the jar file to the same name as the directory (eg: 1.6.2.mods.jar)
10.Rename the json file to the same name as the directory (eg: 1.6.2.mods.json)
11.Open the json file in a text editor and the line that contains the id (eg: “id”: “1.6.2″) change it to the same name as the directory (eg: “id”: “1.6.2.mods”)
12.Save and close the json file.
13.Start up the Minecraft launcher
14.Create a new profile
15.Select the version that you just created (eg: 1.6.2.mods)16.
16.Select the rest of your settings.
17.Launch the game.
Note: Using a 3rd party launcher such as Magic Launcher may save you a lot of time in managing mods.
Download: Single Player Commands
Minecraft mods