In a command prompt window, Alt+Space, e, p -- Performs a clipboard paste. This is handy to perform a quick paste at the command prompt without needing to take your hands off the keyboard. (A Paste can also be performed in a command prompt window by right-clicking the window if "QuickEdit Mode" is enabled (in the Properties dialog), or by right-clicking and then selecting Paste from the context menu if QuickEdit is disabled).
Alt+Space, n -- Minimizes the current window. Also, Alt+Space, x will maximize the window, and Alt+Space, r will "restore" the window to its original size after it has been maximized.
Alt+Space, m -- Puts the current window into "move" mode. In this mode, you can move the position of the current window with the arrow keys. This can be useful for retrieving a window which is completely off the current screen (if you had multiple monitors connected and then disconnected the monitor on which the window was located, for example).