A hex editor is a program intended for editing binary files, usually executable program files, one byte at a time. This is useful for machine language programming and debugging at the lowest level. Most, but not all, powerful text editors can also edit binary files, and vice versa.
SED (Stream EDitor) is a non-interactive editor, written by Lee E. McMahon in 1973 or 1974 for the Unix operating system, but now available for most OS's.
Instead of the user moving the cursor on the screen, the user sends the program a script of editing instructions. In this sense, SED works like a filter - deleting, inserting and changing characters, words, and lines of text. This makes it particularly useful in batch files. Its range of activity goes from small, simple changes to very complex ones.
Minimalistic cross-platform text editor by Jon Skinner.
Love it or hate it, vi is the text editor many grow to love. Vi is powerful, configurable and widely available - not just for Unix, clones exist for many platforms.