Sketch - Professional digital design for Mac.
Snip&Sketch - Quickly annotate screenshots, photos and other images with your pen, touch, or mouse and save, paste or share with other apps.
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
NinjaCapture - All in on Screen Capture
Affinity Designer - Professional creative software, exclusively for Mac.
Picosmos Tools - Picosmos Tools integrates picture browsing, editing, layout, frames, and cosmetic effects into one set. It also provides plenty of source material.