This next title is a quick and obvious tool, and I had been holding it back because it seemed a little too simple. This is ascii.
Which, as you can see, either displays a chart of ASCII conversion data, or takes a string of digits and returns their conversion, as would be useful in a script. Escaped characters and control characters are possible too, as well as octal or hex values.
ascii does a few other things that serve in the same kind of situation; check the help flag or the man page for ascii’s second-string tricks.
But … that’s all I can think to do with it. The value in ascii is its quick-fire accessibility to character codes. And beyond that … ? 
Inconsolation 