Fraps allows you to hide or show FPS based on the configuration mode from its own interface. Firstly, you need to select where the FPS will be placed and then use the hotkey assigned to show or hide it. Start the application, then switch to FPS tab and use the Overlay Hotkey to assign a keyboard command to show or hide the FPS in-game.
Download: http://www.fraps.com/download.php
