Silence of the Terminals
An Australian group is currently developing an educational game based on the Torque engine. It is a First Person Shooter in Capture the Flag mode. At key points, multiple choice questions pop up and force the player to answer correctly to move on without penalty.
I evaluated it without an opponent so I can't comment on the competitive play experience but the weapons and navigation are decent.
The current questions are on HTML coding but it could be adapted easily to other areas.
Download the game here.