I just tried gnome-screenshot, which I didn't know about. It fails with an error after capturing an image because it seems it needs the gnome shell and I don't have it (nor unity) but from the man page it seems it's more or less functionally equivalent to shutter. There are two nice things with shutter: 1) the icon that sits in the notification area (or whatever it is called in a given DE) 2) the list of all the previous screenshots taken. They come in handy for those days when I have to capture dozen of images.