FlightGear Flight Simulator: free open-source multiplatform flight sim
A free transportation simulator game
X3D is the open-standard format for 3D graphics scenes on the Web.
Old style soccer game with many exciting features
Online War system for IL-2 Sturmovik and Iron Front in ArmA 2
functions for 2D/3D graphics + realistic driving simulation
Naval trade simulation in the north and baltic sea during 1250 - 1500
3D space trading and combat game
The Clue! / Der Clou!
Random any number you want as many as you want
This is a hacking style game set in the early '80s
The free and Open Source hockey simulator
A libgdx pinball game.