WorldEdit 
WorldEdit is an easy-to-use in-game world editor for Minecraft, supporting both single player and multiplayer, that lets you:
- Change thousands of blocks in an area at once by selecting regions.
- Use over 100 functions to modify the world or remove problems.
- Remove large chunks of land as you wish.
- Sculpt the world and build mountains with brushes.
- Fix annoyances such as broken water, missing snow, raging fires, and more.
Some of the things that WorldEdit can do include:
- Build far away with WorldEdit's original brush tools
- Mine instantly with the super pickaxe
- Use your compass to quickly teleport to areas by left clicking or using /jumpto
- Replace a giant area with a block of your choice
- Choose an area and have it instantly restored from backups
- Level an entire mountain and replace it with natural looking terrain (with brush tools)
- Smooth an entire mountain quickly
- Generate spheres, cylinders, cuboids, forests, pumpkin patches, and snowy areas
- Copy areas, paste them, load them, and save them (compatible with MCedit)
- Kill mobs, nearby or across the world, and remove entities (arrows, items, etc.)
- Find out which chunks were in a region, look up your current chunk
- Count the statistical variation of blocks inside an area
- Ascend through ceilings, pass through walls
- Tie in with WorldGuard to protect areas
