Occasionally, as a developer, I have a need to do a hex dump of a file to inspect extraneous tab characters, extra newlines, etc. On the Mac, you can easily do this on the command line.
With this command, you can get a nice, side-by-side hexadecimal and ascii view of the first 128 bytes of a file without downloading any shareware or other development tool:
hexdump -C -n128 myfile.ext