You can enable the God Mode cheat in Call of Duty 4: Modern Warfare for the PC and do almost anything you want in the game.
1. Press ~ to bring up the console. (Console must be enabled under Options)
2. Type seta thereisacow “1337″ and press Enter.
3. In the game, press ~ to bring up the console.
4. Type god and press Enter.
If you want to enable God Mode but still want the screen to shake, use the code demigod instead.