Well i usually use either emacs or vim if emacs is not available.. But those two editors should only be recommended if one needs their power, their great keyboard interface or just wants to learn the way to edit something in a good way
For Windows, I prefer [url=http://notepad-plus.sf.net[/url]notepad++[/url]. Working in terminal, I prefer vim. I've heard good things about bbEdit for the mac. For Linux with a GUI, I'd go for something SciTE based.