Minako's Transformation Pen
Codename: Sailor V
In Codename: Sailor V, it was given to her by Artemis in the first act in order to transform into Sailor V. The crescent moon on the cap of the pen is a speaker which Minako would use to communicate with "Boss". The decoration on top of the cap could extend into an antenna. The pen also writes what is true and Minako would often take advantage of this fact and use it for passing tests, in which Artemis would disapprove of.
In Sailor Moon, Minako used the pen in order to transform into Sailor Venus, due to her awakening in the last act of Codename: Sailor V. It was also shown to have a connection with the Sailor V game at the Game Center Crown, where it reacted if someone was playing the game well. The pen was destroyed when the Inner Senshi gave up their pens (Minako explained that also meant giving up their lives) on order to reawaken Princess Serenity and Prince Endymion, after Sailor Moon killed herself and Endymion and the Silver Crystal grew over their bodies. It was replaced by her Star Power Stick.
It was used the same way in Sailor Moon Crystal as it was in the manga.