Best editors and IDEs for programming

There are many different editors and IDEs available, like:

Code Blocks, Kate, gedit, Notepad++, Anjuta, Eclipse, Visual Studio, Vim, Geany, Dev-C++, C++ Builder, MonoDevelop, Nano, Qt, KDevelop, ... (and Delphi, FPC, Dev-Pascal)

Which one do you use?

Which one is the best?

I need an interface which has a good code completion.

C++ Builder is available only in Windows. Does anybody use it? Is it useful? (C++ Builder's editor is really powerful, but it's compiler is not g++ or gcc. That's my problem.)