The D.O.S. is a fictional weapon in the 2007 video game No More Heroes. It is a beam katana constructed by an infamous Japanese hitman, and one of the more dangerous models to use. The blade of the D.O.S. activates the instant its handle is removed from its scabbard, and the beam katana features no off switch in its design. This makes the process of refitting the blade into the scabbard extremely difficult, as well as unsafe. Also, the end of the handle from which the blade projects resembles a power plug. The design of the D.O.S. itself bares a resemblance to a shirasaya, a plain Japanese blade mount.