Just click the Capture menu and you will have the commands Selection, Window, Screen, and Timed Screen.

It will let you do screen shots with your mouse instead of having to memorize the shortcuts. OS X comes with an app called Grab (as in 'screen grab'), in your Utilities folder. The fact is that the Mac came out with a 'snipping tool' app way, way before Windows ever did. When people tell you the Mac keyboard shortcuts for screen shots, those are actually only the shortcuts to a much deeper set of screen shot capabilities. So, There is no ap for that! Too bad, trying to remember all those key board short cuts takes some of the glamor out of Apple.