[PyWoody]

If you don't need to edit the screenshot, Command+Control+Shift+4 will bring up crosshairs that will put the screenshot selection in your clipboard and won't save it to disk. It's super handy for doing a ton of quick, one-offs.

[MontagFTB]

If it helps, hitting the spacebar will toggle screenshotting a window.

[agos]

and it includes the shadow, with trasparency! looks great