According to Apple, the S in iPhone 3GS stands for "Speed." Back in 1986, the S stood for "Sound," and the "G" stood for "Graphics." It was the Apple IIGS, the first Apple with a colour graphic user interface.
The GUI was influenced by Lisa and the Macintosh, and—with its 16-bit architecture, megabytes of RAM, and wavetable music synthesiser—it directly competed with the Commodore Amiga and the Atari ST.
In fact, it was so cheap—$US999—and fast that it competed with the Macintosh itself. Not only that: The Apple IIGS was backwards compatible with the Apple II and its huge library of software titles, which made it even more dangerous to the success of the Mac. During its first year of production, the Apple IIGS sold more units than all the other Apple products, including the Mac. Many argue that this is why this cool computer was killed.
Extra bonus points cool fact: There was a limited "Woz" edition made to celebrate the 10th anniversary of the mighty and beloved Apple II, with Steve Wozniak's signature stamped on the first 50,000 units. [Apple IIGS information from Wikipedia]