I have recently found out about it, and it’s much faster than ffmpeg, maim, scrot, and shot.

With an image like this

• ffmpeg takes 0.349 seconds
• maim takes 0.970 seconds
• scrot takes 0.338 seconds
• shot takes 0.844 seconds
• shotgun takes 0.259 seconds.

and with an image like this (200x200+1440+0 geometry)

• ffmpeg takes 0.747 seconds
• maim takes 0.018 seconds
• scrot doesn’t allow you to provide a custom geometry, so I can’t do a fair test (Also, when using the selection option it sometimes leaves white lines in the screenshot)
• shot takes 0.063 seconds
• shotgun takes 0.018 seconds

I personally use crud for making a selection.