I'm new here, stumbled into this challenge and decided to give it a go because I'm testing some simulation software anyway. I realize this is pathetic compared to some brilliant entries I've seen but this is a little tongue-in-cheek...
I'm purely interested in the simulation aspect of it all and this is 100% dynamics, 0% keyframes and... a few bricks are actually knocked down!
I didn't even know about trebuchets, obviously a lot of research about the subject is needed. So, this is more like a toy... a spoon with a weight and some bricks.
Software: Realsoft3d 4.5 and Dynatomics beta (!).
I'm still learning the more advanced features of Dynatomics; next step after the trebuchet research wiil be addition of a sling and a cloth basket, hopefully its reach will improve a bit ;-)