Surprisingly, in most cases, a control system in AR games is not a major issue. Players move the camera over a virtual scene, so there is no need for special controls to maneuver in space. Thereby, many AR shooters only have one major button: FIRE. So, it is more interesting to know about a situation when fiducial markers are turned into tools to manipulate a game situation.
There is a difference between AR on mobile devices and some academic experiments that use optical head-mounted displays to produce AR. The latter usually needs a player to hold a gameboard with fiducial markers in his hands, tilting and moving it, since the gameboard is a way to control objects and events in a game.
A very good example is Marble Game, designed by Ohan Oda and Steve Feiner at Columbia University's Computer Graphics and User Interfaces Lab (http://www.youtube.com/watch?v=6AKgH4On65A), where players needed to guide a ball through a maze. A special game board with ARTags was used as...