This is a showcase video of a working trebuchet that I made in Minecraft. You can fire and reload it but for the moment it doesn't really have any use other than for aesthetics. In real life this was used as a medieval weapon for besieging castles. Sadly the create mod doesn't know how to fire anything yet. If you fire the arm at a high speed you just fall trough. If you do it slower you can stay on the arm but you don't keep your forward momentum when you're at the top and you just fall down.
timelapse of building the castle:
https://www.youtube.com/watch?v=ZySLVWp7lt0&t=411s
download Create mod:
https://www.curseforge.com/minecraft/mc-mods/create/files