A word to describe those people that LOVE stationery. It is a portmanteau of 'pen' and 'enthusiast'. It is a pretty self-explanatory term: an enthusiast is person who is highly interested in a particular activity or subject and in the case of a penthusiast the subject is pens. And all their 'cousins'. (i.e. highlighters, erasers, hole-punchers, etc.)
Such people would move into an Officeworks store in the blink of an eye if given the chance.
Abby: So what are you getting Ursula for her birthday?
Mavis: I got Ursula this massive box of Crayola Crayons and some Derwent charcoal pencils.
Abby: ... Will she like those?
Mavis: Oh yeah! She's a total penthusiast. She could live in Officeworks! If you want her to fall in love with you forget sending chocolates and roses, send her post-its and blu-tac.