Hattori's Katana is a meleeweapon which has a special charge attack that will be activated if the attack button is held down after an attack. The charged attack deals critical damage.
"All uncharged attacks deflect bullets (but not grenades)."
Synergies
The mutation Predator can be used to turn invisible, to more safely initiate the fourth hit.
The mutation Melee can be used to Slow down targets, to more safely initiate the fourth hit.
The fourth hit of this weapon deals high burst damage, allowing for great healing with the mutations Frenzy and Adrenaline.
Notes
The fourth attack shown in the details section of this page represents the charged attack, however, the charged attack can be initiated at any point in the combo.
The fourth attack ignores the spiked backs of the Thorny, but no other shields.
The damage from the charge attack comes directly from where you stop moving, meaning that if a Shieldbearer is facing you when you start the charge, it will damage the Shieldbearer once you finish. This works the same way for every other enemy that can block attacks.
Holding 2 of this weapon with a legendary and normal version will let you do 2 consecutive crit dashes with the right timing, with the second attack traveling a bit less far. The timing is precise and you must hold the other attack button immediately after the red slash at the end to execute the second consecutive crit dash.
Because of the large vertical range on the charged slash it is possible to strike enemies not too far above or below platforms, such as Kamikazes which very often hang from thin platforms.