This is a basic character frequency counter. It will count each instance of an ASCII or extended ASCII character, and will give a total of the number of Unicode characters.
I originally wrote this in VB.NET years ago as extended ASCII and Unicode characters were causing me some issues. This was a quick way to find them as it would give me the counts for however many there were as well as highlight them in the input text box so that I could easily find them.
When I started using Linux, I rewrote this in Python using Tkinter for the GUI. This was my first application using Tkinter. I later learned Gtk + Glade, so I re-wrote this again using that for the GUI.
I'm including both versions here as they are essentially the same application, just with a different GUI language. I thought that this might be useful to someone either as an application by itself (I still occasionally use this), or as an example of the differences between Tkinter and Gtk.
Update: I included a screensshot of both versions.