Project Orcon (short for organic control) aka Project pigeon, has to rank as one of the most outlandish weapons projects of the 20th century. It was the brainchild of American animal behaviorist Burrhus Frederic Skinner, and built on his own work on operant conditioning in the 1930s.
The Gist of the device was to place three specially trained pigeons into compartments in the nose of a missile where pressure sensitive screens would display images of what was in front of the missile projected through lenses in the nose cone.
Provided the missile was fired in the right general direction so the target was visible, the pigeons would then peck at its image on their individual screens. If the missile was off target the pecks would be to one side of the screen or the other, and this would cause the missile to correct its course in the indicated direction. Steering was by majority vote just in case one of the pigeons should panic.
Skinner had notable success in training his pigeons, but a good deal less success in getting anyone in the military to take his idea seriously. In the end the development of reliable inertial guidance systems rendered project Orcon redundant, and Skinner went on to prove that his pigeons were capable of forming superstitions. Which given how close they had come to being fired at enemy ships on the end of rockets shows they were a good deal smarter than a lot of people gave them credit for!