TextWrangler.

Version 4.5
Great `grep` flavor.
Fewer calories.

Winner, Macworld Magazine
2013 Editors’ Choice Award.

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BBEdit

The leading professional HTML and text editor for the Mac, with high-performance features for editing, searching, and manipulation of text.

The simplest way to organize all the small (or even large) bits of information that you use all the time on your Mac and iPad.

The super-powerful all-purpose Mac text editor and UNIX server administrator's multitool. Oh, and like the best things in life? It's free.