You can find a large list of games with six degrees of freedom on the Track IR developers web site, Natural Point HERE. Following the link will also show the attributes each game supports using the Track IR i.e. Yaw, Pitch, Roll and the coordinates X, Y and Z Not all of the games I've listed below supports all six, i.e.America's Army only supports Yaw and Pitch, however, most games listed do support all or most of the attributes.
Track IR is brilliant because it allows the user to look around in their gaming environment, for example plaing ArmA 3, I can look behind me just by turning my head, lean forwards to zoom in and move my head to the left or right to look around corners. When playing flight sims, especially combat sims, it's a must have as you can look over your shoulder in game without having to use your keyboard, freeing up your fingers for more imortant functions.
I'm really looking forwards to playing Descent: Underground with the Track IR. Once you've used a Track IR you'll wonder why you've not used one since they became available over a decade ago, they really enhance game play significantly.
You may have 6DOF for your field of view, but that's not the 6DOF of motion I was looking for.