Rise of the Triad
To disable the hud, first go through the menus and find the option to enable the console. Then, while in game, open the console with '~'. To toggle the hud on/off, type:
To bind it to a key, open the console and type:
setbind <key> <command>
For example, to bing the 'h' key to toggle the hud, it would be: setbind h showhud
Then press the 'h' key in game to turn the hud on/off. This disables the crosshair too, which makes the game more challenging, so I suggest lowering the game difficulty (may require you start a new game). The hud will reappaer every time you go into the menus and then return to gameplay, so binding it to a key saves a lot of time.
Entering the command in game will save the key binding to the following file in Windows XP (not sure about later Windows versions):
My Documents\My Games\Rise Of The Triad\ROTTGame\Config\ROTTGame.ini file
You can also manually enter the following line to that file:
Replace "H" with the key of your choice.
The following image was taken by the developers.