TrID - Allows to detect file type by recognition of binary signatures.
HxD - HxD is a carefully designed and fast hex editor which, additionally to raw disk editing and...
TrIDNet - TRIDNet is the GUI version of TrID, probably more practical to use than the CLI version, especially...
WinHex - WinHex hex editor, disk editor, RAM editor. Binary editor for files, disks, and RAM. Download HEX EDITOR. Sector editor. Drive editor.
Toolsley File Identifier - Identify files based on the libmagic database in your browser.
Hex Fiend - A fast and clever open source HEX editor for Mac OS X.