On-Screen Ruler - lightweight, free, semi-transparent ruler
System Color Picker - Pick colors from anywhere using the built-in color picker.
Bluegrams Screen Ruler - A lightweight and configurable ruler tool for Windows Desktop.
Sketch Palettes - Sketch plugin to save and load colors into the color picker
Pixus - Pixus is an AIR pixel ruler application, a handy tool for web and interface designers.
Pika - 100% ESM. A new kind of package registry that does more for you. Write once, run on any platform.