An Ultimate Agent's weapon (究極のエージェントの武器) is a device that is used to defeat a source of great evil or destroy a dangerous object. They were created by the SuperSpy Agency 25 years ago. Nobody knows who created them or for what reason, though.
Cookie Jar: from Luigi's Crazy Adventures, the first "episode" of SuperSpy Luigi.
Power Glove: Wielded by Luigi. The buttons on it have different abilities and is also used in his SuperSpy Mode.
The Mario Head: A living Agent's Weapon created by Weegee. It was defeated in Season 1's Finale.
Waluigi's Van, which can fly with rocket boosters. It blasts candy lasers.
The Porygon Tank, a weapon only found in Electric Space. It's purpose is unknown for now.
The Sacred Treasure, used to defeat the Samson Buds/Luigi Clone. Wielded by Luigi
GrandMaster Coin, a Coin with the ability of infinite spending capabilities.
Win Button, a button at the top of the screen in the final battle in Hotel Mario: Preschool Fun