The text editor with which the Angels in Heaven code C.
It is small, fast, and has hundreds of time-saving features. Best of all, it doesn't ship with an annoying paper-clip that tries to tell you what to do.
vi has a steep learning curve that keeps MS using morons far away, but there is a Wintel port so that true Geeks can feel at home if the must be on an M$ box.
MS Word? Notepad? What are those? I only have time to vi.