Here's one that you probably didn't see coming. Nintendo will be releasing Mario Kart 7, the latest portable entry in its long-running kart-racing franchise, for the 3DS handheld on December 4 in North America. Hori, maker of awesome coin-op-style fighting game joysticks, took notice of this fact and got to work on a mount for your device that essentially turns the whole thing into a big steering wheel.
The wheel of course takes advantage of the built-in accelerometer that the 3DS is equipped with. That means its meant for a motion-based control scheme, which in turn means that you probably won't be using 3D for the game if you plan to use the wheel. It does offer larger L and R buttons as well though, which the giant meathook-wielding people of the world will probably appreciate.