SynalyzeIt

Synalyze It! is a simple to use Mac OS X app which lets you easily edit and analyze binary files of any size.

It's the little brother of Synalyze It! Pro but still much more than a regular hex editor.
Synalyze It! features enhanced support for many character encodings and it will allow you to interactively define grammars for various file formats. Several grammars do already exist and can be downloaded for free.
Synalyze It! is perfect for editing saved games or other unknown binary file formats and actively supports reverse engineering.
Here are some key features of Synalyze It!:
* Hex Editor & Viewer
* Printing
* Histogram view
* Go to Position in file
* Save selected bytes
* Compare code pages
* Incremental text search with encoding selection
* Find text
* Find numbers
* Search for masks
* See all strings in a file