[Petya V4sechkin]

screenshot-cmd (первая ссылка из гугла).

[Foreigner]

Starter1,
must have в любом случае.

[Iska]

NirCmd - Windows command line tool, команда savescreenshot.

[kiripanda]

IrfanView, ключ /capture

Код:

Example for capture:
  i_view32.exe /capture=0
  => Capture the whole screen
  i_view32.exe /capture=6
  => start in Capture mode, use last used capture dialog settings
  capture values: 
  0 = whole screen
  1 = current monitor
  2 = foreground window
  3 = foreground window - client area
  4 = rectangle selection
  5 = object selected with the mouse
  6 = start in capture mode (can't be combined with other commandline options)
  Advanced examples:
  i_view32.exe /capture=2 /convert=c:\test.jpg
  Capture foreground window and save result as file.
  i_view32.exe /capture=2 /convert=c:\capture_$U(%d%m%Y_%H%M%S).jpg
  Capture foreground window and save result as file; file name contains time stamp.