In epic movie Gladiator, Maximus says to his men, "at my command, unleash hell!" Well and minutes later Roman Terbuchets indeed rain fire on Germanic tribal army!
If you always wanted to find yourself in that battle on the screen, here is something that could delight you. You can find numerous blue print plans of the Terbuchets online or could even purchase a kit to get yourself started.
Scream, "For Rome!" as you release your first fire ball!