The uses of most of the keys you have pointed out on this thread have been mentioned, but a few have been missed
Pause/break: Used to pause really old games (not used for that any more) also you can press windows key+pause/break to view your computer specs.
Still not sure what the `~ key does or the scroll lock.
However, one thing that no one has mentioned is that thing between the windows key and ctrl key (on the right side) I have no clue what it is and I have a picture that I googled to show you.