You can't write the word "fight" while fighting someone-using a pen against them while they fought using a pencil! Even if you have a piece of paper in the other hand.
What would happen if someone figured out how to? Well, the pen could never be able to avenge itself unless it somehow found a way to "write" back...
One question, though, before you go: would the pencil's wits be sharpened during the battle?