Me and a friend made a fun little game and managed to get it greenlit and then published on Steam. It is 99.99% custom made including the 3D engine and physics, we decided to make the source code available to those that buy it.
Anyway thought it might tickle a few people 
http://store.steampowered.com/app/467790/
If anyone has a go at modding it we are happy to help, really want to see what people come up with