Kupfer is a command launcher, that is not only capable of starting applications but also supports file operations, web searches, media control and much more. The reason for its diversity is the number of available plugins. Kupfer is written in Python and has a flexible and well designed Plugin-API, which makes it easy to extend its functionality.
I have written a few plugins for Kupfer so far, which can be found in my Github repository for Kupfer Plugins, of which File to Clipboard turned out to be the handiest. Whenever you want to open or save a file need to specify its path. With Kupfer, one can quickly navigate there (faster than I can with a file browser or even the terminal) and then, using my plugin, copy the file's or directory's path into the clipboard for pasting in the application of interest. Moreover it can copy a file's content to the clipboard which I have not used that often to be honest.
Make new Directory does exactly what its name suggests: I creates subdirectories in the directory that is currently selected in Kupfer.
Parent Directory simply opens the directory a file is contained in via the system's file browser.
Todo.txt is a plugin to add tasks to Gina Trapani's super handy Todo.txt task manager. Note that Go For It! uses the same format to store todo lists, so they can be used in conjunction.