Microtransaction Gun

 is a gun that fires gems, books, money, and figurines of the Gungeoneers in exchange for one per shot, listed below.

This gun can also be unlocked immediately by buying the Collector's Edition, or the relevant DLC.

Trivia

 * The expression "Pay To Win" is derived from micro-transaction-heavy games, where an advantage over other players can be achieved by investing more money in the game.
 * The green crystals this gun fires and uses as its ammo counter may be a reference to "Dungeon Keeper", an iOS game by EA which famously blocked player progress unless they separately purchased green crystals which would greatly speed the game up.
 * The Microtransaction Gun is available as an added DLC on Steam, thus allowing players to make a microtransaction to obtain the Microtransaction Gun immediately rather than unlocking it normally through gameplay.
 * Since the Microtransaction Gun's max ammo and current ammo are both equal to the player's, it always reads "Full" if the player tries to collect an ammo box while holding it.
 * The Microtransaction Gun is the second most expensive item sold by Ox and Cadence.