The hihex utility works like the 'hexdump' command with a special addition. It allows you to view the character output of ASCII values that have the high bit set.
This is particularly useful for examining binary files from older computers, such as the Apple II, where they would commonly use the high bit versions of characters to display text in other modes such as inverse.
Also great for diffs!
#Still don't get it
Here's a quick example. Look at this file with hexdump...