The Atari Lynx was the first hand-held video game system in color. Though it never took off due to Atari's plethora of corporate troubles, it was way ahead of its game (pardon the pun).
A little-known company named Epyx created the Lynx in 1987, when it was known as the "Handy". Atari bought the Lynx and it was released in 1989 (the same year as the Nintendo Gameboy). Later, there would be a Lynx II revision to solve some problems with the original. The original Lynx package (the "Deluxe Package") included the system, California Games (I still have nightmares about that game), a carrying case, an AC Adaptor, and a ComLynx cable (which allowed multiplayer capabilities). The adaptor was later replaced by 6 AA batteries. Of course, there was also a core package consisting of just the Lynx. Years later, there was also a special deal with the Lynx and four games, but it was mostly a clearance scheme.
Physically, the Lynx was very similar to the Game Gear in dimensions. The screen was 3.5" big (diagonally, of course). There were two fire buttons, A and B, two option buttons, Option 1 and Option 2, a Pause button, two power status buttons, Power On and Power Off, and a Backlight button (on the Lynx II). There were volume and brightness controls, a headphone port, a ComLynx port, and the mandatory power port.
The Lynx had two 16-bit co-processors running at 16 MHz each, nicknamed Mikey and Suzy. Mikey supported the sound engine and the video driver, the system interrupts routine, ComLynx support, and the system timers. Mikey was also responsible for loading the games with the 512 bytes of ROM it had for that function. Suzy supported the graphics engine and a math co-processor. The Lynx contains half a megabit of ROM. Game cards support up to 2 MB of ROM, but most contain either 128K or 256K, with only 3 games supporting 512K.
The Lynx is widely regarded as one of the best, if not THE best, hand-held gaming systems of all time. It is not until recently that other comparable systems have given the option of multiplayer play (Lynx supported up to 18 players!). The backlight is a still-demanded feature in the Gameboy. By reading the specs, you must give Atari a lot of credit - they really maxed out the system, and this was nearly 12 years before this writeup. You can still manage to find Lynx'es for sale online, if you're willing to pay the money.
Technical specs courtesy of www.atarilynx.com.