maim - maim (Make IMage) is a spiritual successor to scrot — a simplistic CLI-friendly screenshot tool.
Nimbus Screenshot - Take screenshots and record video from your screen
Flameshot - Powerful yet simple to use screenshot software for Linux.
Snagit - Screen Capture Software for Windows and Mac
Gnome Screenshot - GNOME Screenshot is a utility used in the GNOME desktop environment for taking screenshots.
CloudApp - CloudApp allows you to share images, links, music, videos and files. Here is how it works: choose a file, drag it to the menubar and let us take care of the rest.