Hercules Graphics Card
The Hercules Graphics Card (HGC) is a piece of hardware which gives IBM personal computers higher display resolution than their default capabilities. The card was developed in 1982 by Van Suwannukul so that he could display the Thai alphabet on the screen. Hercules graphics use the same 720×350 resolution as the text-only IBM Monochrome Display Adapter, but allows for custom graphics as well.
By the time I got into computers, EGA was already standard, and VGA graphics had just been introduced. I think I only ever saw Hercules graphics once at my step-father's office, but I never used it. It wasn't until DOSBox started emulating it that I became more familiar with the output.
Hercules Graphics were not nearly as popular as CGA graphics which came out a year earlier, but it did support a resolution almost twice the size of CGA's color mode, and larger than CGA's monochrome mode. However, few developers drew completely new graphics for HGC, and usually used a driver to scale up their color graphics and convert them to dithered black and white. Here are some screenshots of Hercules graphics for popular games.