Ftype

I found this command useful and think it deserve some PR.
I know, you can have a full rich IT life without using it or even knowing about it BUT when the day come it can save you hours of work.
Ftype is a command line that displays or modifies file types used in file name extension associations.
The basic command displays the file types that have open command strings defined.

c:\ftype

The output is long and descriptive.
Ftype is very useful in scripts, installations that involve unique file extensions but also when you work on a PC and have problems. When you start going out of the mainstream Microsoft based applications many programs use different file types that are different from the default MS installations. Locating the missing file extensions is much easier using this command hence it is good to be familiar with it.

Here you can find a greate example for a good use of this command