Oolite is a space sim game, inspired by Elite, powered by Objective-C and OpenGL, and designed as a small game that is easy for users to pick up, modify and expand upon. It is a freeware game application.
Here are some screenshots to illustrate the features and user interface of this application:
Second Life
FlightGear
1939:BATTLEFLEET
Live for Speed
Guns, Girls, Lawyers and Dollars