When the Pen is Mightier Than the Sword (and when it’s classified as a deadly weapon)

In cinema, a writing instrument being used as a weapon is not uncommon.  Normally, this occurs when the writing implement is in the hands of, say, an experienced killer:

3.  Jason Bourne uses a pen to gain advantage in a fight in The Bourne Identity.

2.  Martin Blank uses a pen to kill a man in Grosse Point Blank

1.  The Joker’s pencil trick from The Dark Knight

But, I’m not sure how this case fits into all this.