Arquebus - a "basic" firearm, with all the associated characteristics.
Sniper Arquebus - greater range and possibly damage, but lower rate of fire.
Heavy Arquebus - greater damage and armor penetration, at the cost of range (?).
Hand Cannon - an AoE weapon.
Portable Cannon - less maneuverable, but a more long-range or higher-damage version of the hand cannon.
Tanegashima - press X to win.