AckCon is an annual event in Bielefeld, Germany, where (partly former) 3dgs users meet. We usually end up creating a game over the course of one weekend using the acknex engine. You can download and play most of the games here:
https://vksbm.de/ackcon/

Except for the 2015 game they're all in English. I like 2014 (Ackmania: Operation Deadnex) and 2013 the most. Last year's game was accomplished by only five people, including code, art and music.