When I started developing on the Mac, I was of course in the need of a capable hex editor. Even now there is no such comparable with what can be found on Windows. In the English Wikipedia, there is a useful Comparison of Hex Editors.
Since ordinary hex editing is not what I was looking for, I concentrated on the hex editors with "file structure view" (see second table on the Wikipedia page). If you're searching for a tool that disassembles machine code, this page is probably not for you while some of the applications do support this.
When I digged deeper and checked what the applications are really able to accomplish, only these products remained in my list (all on Windows only):
Additionally should be mentioned DataWorkshop which has some nice ideas but is completely outdated - not able to open and process large files and not really intuitive to use.
On the Mac there are only PeekIt and iBored offering more than simple binary file editing, the others (Hex Editor, HexEdit, hexedit, 0xED, Bless, beye, Hex Fiend, MadEdit, wxHex Editor) all don't help you much to understand what's encoded in a binary file. For PeekIt you can write a plugin for file analysis if you're a developer. The good thing all Mac application have in common: they're free :)
By far the best and complete hex editor I've ever seen is 010 Editor. Not only does it have many sophisticated features like searching for floats with tolerance or exporting tables to CSV files but it provides the best way to analyze a file by describing its structures and contens in binary templates.
Now for Synalyze It! the mission is clear: become as powerful as the best tools on Windows while retaining attributes a typical Mac application has: intuitive to use and focused on a certain audience.
I was missing two more (older) Mac tools for editing of binary files: