Activating this trainer:
Press F1 at main menu.
Listen for 'Trainer Activated'.
Press desired hotkey. All hotkeys can be changed on the trainer.
Numpad 1: God Mode
Numpad 2: Unlimited Ammo
Numpad 3: No Reload
Numpad 4: Invisible/Disable AI
Numpad 5: No Recoil
Numpad 1: God Mode - toggle on and most things cannot kill you.
Numpad 2: Unlimited Ammo - toggle on and when you reload, you have plenty of ammo.
Numpad 3: No Reload - toggle on and when you fire the weapon it will have 9 rounds.
Numpad 4: Invisible/Disable AI - wait until the mission starts, then toggle this on and you can move about the mission and the AI in the game will likely ignore you and remain in position. You can toggle this on and off when you want to move about hidden. While this is on, if you have not been spotted by humans, you are invisible. Cameras and etc. will still see you, so plan accordingly.
Numpad 5: No Recoil - toggle on and most weapons will not recoil when you fire them.