All Symbols - While playing press Shift+Alt+J for all symbols.
All Weapons - While playing press Shift+Alt+W for all weapons.
Command-line Codes - To use these codes start your game with one of the
following command lines:
TEKD1 NOCHASE-Removes the shooting enemies from the game.
TEKD1 NOENEMIES-Removes everyone but you.
TEKD1 NOGUARD-Removes the guards from the game.
TEKD1 NOSTROLL-Removes the innocent bystanders from the game.
God Mode - While playing press Alt-Shift-G for all weapons and
invulnerability.