Mini catapult... this could be something really fun to make for a lesson that is a collaboration with a history class. Students could make this one, then take what they learned to design a different one! This definitely promotes students' skills in analyzing, problem-solving, and collaboration with each other!
A knights weapon of choice was usually the sword, but swords were difficult to forge and maintain. This picture shows a variety of the other weapons that a knight would use in battle http://www.medievalages.net/2013/07/medieval-weapons/