GHex can load raw data from binary files and display them for editing in the
traditional hex editor view. The display is split in two columns, with
hexadecimal values in one column and the ASCII representation in the other.
A useful tool for working with raw data.
GHEX
LFHEX
WXHEXEDITOR
VELES (github, not developed now, nice 3D visualizations, full featured for analyzing of unknown data structures with support for png, zip and other)
If you're using KDE, Okteta is the way to go.
Try GHex
From the app's Github page:
sublime is a good choice and it is multi purpose editor.