Automatic aspect ratio

4:3 aspect ratio
16:9 aspect ratio
16:10 aspect ratio
5:4 aspect ratio
Automatic wide aspect ratio
Aspect ratio: automatic
Anamorphic
Letterboxed
Widescreen
Customizable aspect ratio
Customizable anamorphic aspect ratio

This is mostly useful for games running in a window, allowing the user to shape them as they see fit, but it also helps making games more portable to more exotic hardware where regular aspect ratios may not be of any use.

Some games have limitations on vertical or horizontal pixel resolution due to non-scaling graphics or static UI design, but with sufficiently high resolution almost any aspect ratio can be possible.

Generally any game that accepts (almost) any resolution and automatically adjusts the graphics to it, mostly how 3D scenes are projected, but also covers 2D scenes (both experience a stretching effect with incorrectly handled aspect ratios otherwise).