One of the very cool new tools in Illustrator is the Eraser tool. To see how it works, select some of the objects on a page and choose the Eraser tool (Shift+E). Click-and-drag with the Eraser over the top of the selected objects, as well as unselected objects. It will look as if the tool is erasing everything that it runs over, but when you release the mouse, only the parts of the selected objects that you erased will be gone. Similar to the Knife tool, the Eraser divides all selected shapes into separate objects that are not Grouped. You can change the shape, size, and angle of the Eraser by double-clicking on the tool itself, but that’s another tip.
Tip provided by Jeff Witchel, Certified Adobe® Training Provider.