Ignis is the kind of person who refuses to use anything but the sharpest pencil, if he must use a pencil at all (he prefers nice pens). He refuses to use mechanical pencils because the lead breaks too easily, and will compulsively sharpen wooden pencils every few paragraphs or so.
Once, Noctis or Prompto swapped out his pencil with colored pencils and he was too busy/tired to notice until he’d started working on a draft of some official document and it came out purple.
Of course, being Ignis, he’s also found…creative ways to use pencils in more naughty ways. He’s found they make especially fun toys when a certain sensitive Shield is blindfolded, because they can provide so many different sensations in one go and Gladio can never quite figure out what it is. Ignis particularly enjoys writing “I love you” on Gladio’s side with the eraser because it always makes Gladio squirm. (Guess I’m in a Gladnis mood tonight…)