A Seej engine.
"Snoozing on his throne, the last sound Lord Aethelred heard was a flaming cask of night soil splintering the Great Hall's rafters."
--Qie Zi, The Art of Seej
The Penny Mortar will loft a U.S. penny over the sofa with contemptuous ease.
The zip file contains all pieces broken out so that international Thingiversians can scale the nock for their local coinage.