I work in a few different editors based on what I'm doing.
Anything config/system related: Vi/Vim (comes on every unix based system) (
http://www.cs.colostate.edu/helpdocs/vi.html).
Java: Editor (see below) or NetBeans (FRC) or Eclipse (Professional work)
C++: Editor and Xcode
General: TextMate (
http://macromates.com/)
I've also used/know people who have used the following editors:
BBEdit
Sublime
Nano
TextWrangler
Fraise (
https://github.com/jfmoy/Fraise)
Adobe Brackets (for html/css work)
Notepad (don't use this one)

(Please don't use it)
Microsoft Word (I'm not kidding, never use it)