A stungun 20 times more powerful than a police-issue device was found by Napier officers on a drugs and firearms bust.
The stungun, which can deliver a 100,000-volt jolt, was built by a company in the US, where they are legal in several states.
Police said they were alarmed to come across the devices, designed to look like a cellphone.
They are classed as a restricted weapon in New Zealand and unlawful possession can result in a jail term up to three years and a fine up to $4000.
The two houses police targeted were occupied by people police described as having "gang connections".
"It is very concerning," Detective Sergeant Heath Jones of the Napier Law Enforcement Team (LET) said of the weapons haul which included two shotguns, a rifle, a semi-automatic 9mm pistol and four stunguns which were found at the Tamatea property.
Also uncovered were parcels of cannabis with a street value estimated at $9000.
Mr Jones said the occupants of the house were a woman and her daughter and that it was likely being used as a form of "safe house" storage spot by others.
The woman had not been charged but was assisting police in their investigation.
Mr Heath said he expected arrests to result from follow-up inquiries.
One of the shotguns uncovered had been reported stolen from Westshore in August, and a man had been arrested over the burglary at the time.
'Inquiries showed the pistol had been reported stolen from a house in Porirua in 2000.
"It shows that this sort of stuff floats around."