My recent playing with the Gameduino had me thinking more about games like Space Invaders, and while I was searching around for bitmaps, I kept thinking about the sound effects. I didn't realize this, but they were not digital sounds, but sounds produced by triggering a series of analog circuits. The schematics and some analysis of these circuits can be found at the following page:
It should be possible to use LTSpice and its own ability to write out WAV files to directly simulate these sound effects. This is of no real relevance to the Gameduino, but it is interesting in its own right.