Historical note: There's a castle in France with a collection of medieval weaponry. It's weird to see several huge trebuchets standing on the battlements. (On a much smaller scale, my son in law built a model with my grandson, and once they got the range adjusted they could hit their target reliably, time after time. Of course they used same sized ammo: got them at the supermarket in cartons of twelve.) The real ones threw stone balls, but could also fling things like rotting animal carcasses, hornets nests, or even the heads of captured prisoners. Something like that could really demoralize the defenders, I'd think!
On the show Northern Exposure, they once built a trebuchet and flung a piano.
/Junkyard Wars/ a.k.a. /Scrapheap Challenge/ had heavy-object-flinging tasks several times. I remember washing machines, and even cars. Trebuchets were usually the winning solution.