Soldier of Fortune
To disable the hud in Soldier of Fortune, create a shortcut to the game. add "+set console 1" to the command line after the executable.
When in game, press ~ to bring down the console and enter the command: scr_interface 0 to disable the hud (scr_interface 1 to re-enable).
The setting should hold with restarts. If it doesn't, go to Soldier of Fortune\user\ directory and open the config.cfg file.
Find the line:
set scr_interface "1"
change it to:
set scr_interface "0"
Save the file. If you can't save the file, you have to change the file properties. Often times if the file is marked as read only, it won't save changes.