The edge of many clickable buttons in various GUIs. Beveling makes them look as if they had been hewn out of solid material and are actually a few pixels "tall", coming toward you through the fourth wall.

The simplest bevel in computer graphics is to surround a rectangular area with a border that is light on the top and left, and dark on the bottom and right. This is done so often that your brain accepts it as a bevel. Look at, for example, the Start bar in a Micros~1 Windows GUI.

It's gotten to the point where many users won't realize they can click on something unless it's underlined or beveled.