In the good old days of the West, back before they discovered the wonders of gunpowder and what it can do, it looks like wartime weapons in the medieval period were pretty crude, crossbows and all. However, the great thinker Leonardo Da Vinci has also done his fair bit of contribution to this area of warfare with the trebuchet, and you can now build one (non-lethal) version by yourself with the $24.99 Leonardo Da Vinci Wooden Invention Kits: Trebuchet.
This entire kit has been pre-cut, drilled, and is ready-to-assemble (like the Avengers), where you can then come up with your very own trebuchet without having to go through engineering classes and the like. It is the perfect gift for history buffs, teachers, and weapons fanatics, and would require an hour or two of your time, tops. Of course, you will need to make sure that you have a ruler, scissors, some small clamps, and pennies (or rocks) as a counterweight handy before you get started, and this unique DIY trebuchet has a range of 20 feet as well. It will be made from natural untreated wood and plywood with some clay balls accompanying it to destroy those LEGO brick walls that you have built.