The following weapons were used in the film Godzilla 2000:
Howa Type 64
The Howa Type 64 is seen carried by JGSDF troops in the film.
Sumitomo M2HBs appear mounted on various armored vehicles.
General Dynamics M197 Vulcan
AH-1 Cobra helicopters of JGSDF armed with a General Dynamics M197 Vulcan three barreled Gatling gun. The helicopter is most likely not a real one but CGI.