But one of the neat things with the Eraser is some of the edge effects you can get on an image.  With a large brush size and a low Opacity, I can make the edges of the clock look faded, misty looking.  This is a nice effect for some graphic work.

Here is a neat Eraser trick.  Have a two layer image with two different colors.  The first image I have has solid blue over a white layer.  Now click on the little paint brush on the Eraser's Tool Options window.  Just like with the Paintbrush, you can choose custom brushes for the Eraser.  See Paintbrushes for a full explanation of Custom Brushes.  In this case I've picked an angel brush.  With the size at 100 and the Opacity at 100%, look what a neat effect!  Next I tried a yellow layer under the blue layer.