On mac: <CMD> + <Shift> + <4> then pressing <space> will allow you to select a window for screenshot which includes the window border, title, and transparent shadow.
Hold <control> while clicking to skip the desktop and copy it to the clipboard directly.
I remember as a stupid middle-schooler thinking I was being cool showing everyone how many <option>/<control>/<cmd> key combos there are to take the perfect PhotoBooth shot.
PSA: Reminder – option click everything for nice surprises.
(Other tips: holding <Ctrl> will copy it to your clipboard, and holding <Shift> will allow you to select a region.)