Brute Force Cheats

First to do this, you must have at least one weapon that can zoom in and the weapon you want to be able to. Equip the gun that can zoom, press Y to switch to your other weapon. IMMEDIATELY after pressing Y rapidly click the right thumbstick and you should now be zoomed in with your other non snipeing gun.

If one of your characters dies then you can bring him or her back.
Here's an example: If Hawk dies on level 4, get to the next chapter.
Then, save and go to the main menu. Next you need to go to campaign and load the level you just quit out of. Then, when it says select character select Hawk.
You will start that chapter but Hawk will be there and not dead!
(You can use all characters and levels for this glitch.)