Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
Prototyping Tools - Find the Prototyping Tool You Need
ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
iOS Design Kit - The newest library of native iOS templates
LightShot - The fastest way to take a customizable screenshot.
Pencil Project - Single-user mockup / wireframing / diagramming tool