Sega's first attempt at a handheld, the Game Gear was effectively a portable Master System (to the point that Master System carts could be played on it with the Master Gear Converter) with a larger color palette and a backlit full-color screen. This meant that while it was more powerful than the Game Boy, it also ate through batteries at a faster rate, though fortunately it received some rechargeable alternatives to balance this out.
Also known as the Handy Gam*Boy in South Korea and Kid's Gear for its final year or so in Japan.