Mass Effect 2
Instructions should be the same for both ME1 and ME2.
Instructions quoted from: http://www.tweakguides.com/ME_9.html
If set to =False, this option completely removes the HUD, including all text messages, graphical elements and warnings on the main screen - obviously this can place you at a significant gameplay disadvantage. You can still access the main options by pressing ESC, or by pressing the relevant key. It is recommended that you instead use the Showhud console command to toggle the HUD on or off at any time - see the Console Commands section.
Insert the line ConsoleKey=Tilde under the [Engine.Console] section of BIOInput.ini, you will be able to use the ~ key to open and close the in-game command console at any time - see further above for details.
Showhud - Toggles whether to display or hide the HUD
Setbind [Key,Command] - Binds the specified command to the specified key
Use Setbind to bind a key to the Showhud command so you can enable/disable at will.
You can also use the command Togglehud and ToggleCommandMenu. Correct command may be either Togglehud, ToggleHud, ToggleHUD, or togglehud (different capitilization). Unsure of which is correct. For more information, view this wiki:
A more complete mod for Mass Effect 2, with several more options especially made for creating videos / movies without the hud can be found here: