GAX Professional

From Dolphiq Software Development:

GAXreloaded is a powerful application for web designers, graphic designers and everyone else who works with graphics. It contains a colorpicker, a screen ruler, and a screen capture tool.
The colorpicker allows you to view the color value of every pixel on the screen in various formats(RGB, Hex or percents) and lets you sample that color. After you've sampled a color you can export it to Photoshop to use it in your creation, export it to the clipboard in various formats or save the colorlibrary as an .ACT file which can be imported into PhotoShop.

The screen ruler is very handy for measuring objects on your screen. With the screen capture tool you can capture every part of the screen and export the image to Photoshop into a new image or a new layer.