The chainsaw is a powerful close range weapon.
There have been reports of this item being seen at the Argent facility, though there is no known uses for it. Security personnel have been made aware that this item is has likely been smuggled onto Mars and have been directed to confiscate it immediately. As there are no practical uses for it, it must be assumed that this item should be considered a black-market enthusiasts's weapon.
It allows the player to trigger a unique glory kill on a demon (provided that they have enough fuel). Small demons like the Possessed or Imps only require 1 fuel to kill, larger demons like Revenants or Pinkies need 3 fuel and finally Barons of Hell and Mancubi need 5 fuel. Demons killed by the chainsaw will drop large amounts of ammo, almost immediately refilling all ammo. As such, the most intuitive time to use the chainsaw is when the player is low on ammo. However, the chainsaw can alternatively be used to instantly take down a high-priority threat like the Mancubus, which is viable as there are runes like Rich get Richer and Ammo Boost and as the Slayer can get ammunition from even non-chainsaw kills when low on ammunition.
The chainsaw starts out with a capacity of three fuel, but can be upgraded when the player uses an Argent Energy Cell to upgrade his ammo capacity, with each cell upgrading the capacity by one.
The chainsaw's brand is "Painsaw," which may be seen written on the body of the saw.