Forbidden Lego is a collection of Lego designs for models that will never see the light of day in official kits from Lego, Inc.

Forbidden Lego written by a pair of Lego master builders, who used to work in designing advanced Lego sets (e.g., Mindstorms). While they obviously got to work on lots of cool things while they were there, there were certain projects that just turned out not to be suitable to be made into kits released by the Lego company. They wrote the book to give some kind of a tantalizing hint at the kinds of things that go on behind the scenes at Lego, and the kinds of neat things that might get released in a world without product liability suits.

Models described include a catapult and an automatic pistol. Must. Have.