The famous Zheng3 has release the 2015 edition of Seej, the open source catapult wargame. Based on a tremendous amount of play testing and feedback the catapults are now easier to assemble, print in less time, and are far more accurate. The most exciting new feature is the use of 14mm marbles instead of coins. The fortifications also got an update. They now interlock on multiple sides giving them a tighter fit and a more solid defense against the heaver projectiles.
If you aren’t familiar with Seej, Zheng3 describes it this way:
Seej is an Open Source tabletop wargame designed to advance the state of 3D printing through competition and player-directed evolution. Players print their own armaments and fortifications for use in battle. If you can print it, it’s legal to use in the game.