Grafx2

The Internet is filled with all sort of applications that you could use in order to create nice images and graphics. But if you were looking for the very first paint application, then you should try out Grafx2.
Its graphical interface is incredibly old, but the application runs quite smoothly. It's packed with some tools, but don't expect much from it.

Dated graphical interface with some tools

It launches with a date graphical interface, all available tools are displayed at the bottom of the screen. It supports a number of image formats that you can load inside Grafx2.
You can adjust the size of the paint brush and pick from the many available. There's the option to perform a freehand drawing or toggle splines and adjust the curves of lines. You can draw lines or use the spray to make things nicer.

Draw using this paint application

It comes with the option of using floodfill or of drawing perfect circles with tools inside this application. You can use features to create polyfills or filled rectangles.
Spheres and ellipses can also be created using the tools provided. You can make some changes to layers, pick the color and adjust the background transparency.

More features and tools

You can use the lasso feature or adjust effects inside the application. Enable mirror effect, rotate images, deform, stretch, distort, use borders and modify colors. There's the option to pick from multiple effects, like shades, stencils, smears, tiling and more.
It has a magnify mode and one that allows you to add text to your images. You can adjust the resolution of images and use the undo button whenever you want to remove the latest changes that you've made to images.
All in all, Grafx2 is a nice application that works smoothly, but it's quite dated. Still, you could use to reminisce on the features of the first ever paint applications on computers.