Acer Chromebase
Released in mid-2015, the Acer Chromebase was the first all-in-one Chrome OS device to hit the market. The Chromebase is aimed at people who would enjoy an iMac but don't have the budget to buy Apple hardware. It also makes a good choice for computing in places with little space for lots of computer equipment, such as kitchens and nooks.
Acer chose the NVIDIA Tegra K1 processor for the Chromebase, which is a pretty powerful quad-core processor running at 2.1 Ghz. The screen is 21.5" but the active matrix TFT display doesn't quite cut it in a market full of ISP displays (an issue they've resolved with the newer Acer Chromebase 24). One model also features a touchscreen and still keeps the price low at around $400.
Overall, this was a pretty good entry into the all-in-one market for Chrome OS. Those looking for a slightly upgraded experience should probably look at the Chromebase 24, but this original Chromebase is still a good buy, especially as prices have fallen considerably since it was first released.