This is my first post to Classic Castle.com. I recently found out about it from a fellow SEALUG member at NWBrickCON 2005. Some of my work is on Brickshelf under the name justin2576, or on my webpage
Anyway, here is my catapult
Most of the catapults I have seen were either too large for minifigs or were made all out of technic beams and didn't look very medieval. I designed mine to be very compact, so that it could be still used by minifigs, yet still be able to work.
Some features of the catapult:
+crank that fits minifig hands and is geared down to pull back the firing arm.
+ There is a locking mechanism with a trigger that holds the arm back so ammunition may be loaded.
+ Height and distance may be adjusted as well as arc height and length.
Even though it is a very small catapult it is still very powerful. It can easily launch a stone over my castle keep
The best feature is that the catapult fires in such a way that the arm does not hit the cross bar at the top, but rather part of the firing mechanism hits the section at the front. This basically means that the catapult will not fall apart after repeated use. It actually can survive hours of play from kids without any of the parts becoming loose!
Anyway, I hope you like it.
Justin
What else can I say? 
So I can make my own version.
