Macchina magnifica

Da Vinci's fabled lost invention turned out to be a doomsday machine designed and owned by Leonardo da Vinci, and constructed with help from Philip J. Fry who was led to believe it was an unstoppable ice cream machine. The machine was used to attack those on Planet Vinci who had made Leonardo and Professor Hubert J. Farnsworth feel inferior, but it was stopped and presumably ruined by Fry before it killed too many.

Trivia

 * Though its primary purpose is to exterminate everyone who ever made its inventor feel inferior, it also makes ice cream.

Quotes
Philip J. Fry: And I helped! ...wait, you told me it was an unstoppable ice cream machine! Leonardo da Vinci: Ice cream is just a bi-product of the machine. It's primary purpose is to exterminate everyone who ever made me feel inferior!
 * Leonardo da Vinci: Behold, my unstoppable doomsday machine!
 * Biff: Some doomsday machine! It barely killed anyone!