Shield color and opacity
When you click the crop tool and drag the crop marquee over an image in Photoshop you will see a shield around the area of the image that will be removed when you commit the change. You can change this shield color from the Tool Options bar to make it any color you want. For example, click in the color selector and make it white, gray, black. You can also Adjust the opacity of this shield to make it, for example, 100% so it totally masks out the unwanted area of the image. This lets you see more clearly the portion of the image you have selected.
Rotate your crop
Rotate the crop marquee by dragging on one of its handles to change the angle of the rectangle and make an angled crop from your image. This way you can make a diagonal crop without having to first rotate the image.
This option is way too cool! Click the Perspective checkbox on the tool options bar and you can crop an image in perspective. So, drag the corner handles into any four sided shape you like – each corner operates independently of the others when this option is enabled. Then click the Commit button and the unwanted part of the image will be discarded and what remains will be reshaped and deliciously distorted to a rectangle.
You can use this feature to fix keystone perspective problems with images such as tall buildings (which tend to be wider at the base and narrower at the top) or you can use it for creative purposes.
So, next time you select the Crop tool, check out these features and put them to work on your images.