World edit mod(I NEED ONE)

For singleplayer specifically, there is just Singleplayer Commands. But there is also MCedit if you don't mind program based stuff. There is also a mod called Schematica if you just want to utilize schematics. Which by the way, that one usually works on servers too. It is client side, but doesn't aid in destruction of blocks. Just building stuff that has already been built once.

That's the only single player mod that has world edit I think.
But if you really need world edit, why not make a simple server on your computer and just use it on there?