Here is a Nintendo DS made by youtube user blaues01. The hack involves some electronic gizmos and a.... Samurai sword! I am nut sure if the one shown on the video is real, but its impressive.
The hack goes like this: A laser emits a laser beam in front of our Samurai friend. The laser beam activates a photodiode. When the sword cuts the beam (cutting is what Samurai swords does best), the circuitry activates an electromagnet, which pulls down rapidly a "finger". This finger then presses the button on the DS. This is a very good way to practice the sword pulling technique and have fun as well.