The Sterilizer is a combo weapon found only in Dead Rising 2: Case West It is created by combining a Syringe Gun with some Chemicals. The combo card is obtained by Frank after leveling up, but it can be created and utilized by Chuck. In the case of this weapon, there are no special benefits to creating it as Frank other than the fact you will earn more pp for each kill.
Primary: Hold down the trigger and press to make Chuck or Frank manually aim and fire a chemically-coated tranquilizer dart at a zombie. Although the dart will not kill the zombie right away, it will produce a chemical mutation within the zombie's body. This mutation will eventually cause it to suffer a slow, but gruesome death in which either the head or the entire upper-half of the zombie's body will explode. In that sense, each dart is hypothetically an instant kill. Occasionally after death, The larvae that was once inside the zombie's body will burst forth and attack if Chuck or Frank are close to it. The Sterilizer also works on gas zombies, but it takes even longer for them to die (about a full 60 seconds) since they're tougher than normal zombies.
Don't even bother trying to use this weapon on hazard units, security guards, or zombie handlers because the darts will just bounce harmlessly off of them, doing little to no damage to them whatsoever.