Reverse Engineer's Hex Editor is described as 'As the name implies, this is a hex editor. It aims to be a good general-purpose hex editor and to have a wide selection of features for analysing and annotating binary file formats' and is an app in the Development category. There are more than 10 alternatives to Reverse Engineer's Hex Editor for Windows, Linux, Mac and BSD. The best alternative is HxD, which is free. Other great apps like Reverse Engineer's Hex Editor are wxHexEditor (Free, Open Source), wxMEdit (Free, Open Source), Binary Ninja (Paid) and Kaitai Struct (Free, Open Source).
Bless is a high quality, full featured hex editor. It is written in mono/Gtk# and its primary platform is GNU/Linux. However it should be able to run without problems on every platform that mono and Gtk# run on.
FlexHEX is a full-featured hex editor designed to edit binary files, OLE compound files, logical devices, and physical drives. With FlexHEX you can inspect, modify, insert, search, or replace binary, ASCII, or UNICODE data.
DHEX is a more than just another hex editor: It includes a diff mode, which can be used to easily and conveniently compare two binary files. Since it is based on ncurses and is themeable, it can run on any number of systems and scenarios.