At the main menu, press L, L, R, R, X, X, Y, Y, B, B to unlock the cheat menu in Options.
Destroying armored vehicle or tanks
Use Jones to run up to the vehicle or tank. Lay an anti-tank mine next to it, in turn sacrificing jones Temporarily to take out the vehicle or tank.
Use Jones to run close to the tank, then plant a C4. Throw a smoke grenade on the tank, run for the nearest cover, then blow it up.
Have one of your team members run by the tank to distract it. Then, run up to the tank, plant C4, and blow it up (risking your life). You can heal him with the other team member.
Tanks are weak in the following locations: their rear; in front, in between the armor over the tracks; and where the gun barrel meets the turret.
Extreme mode
Complete the game on the hard difficulty setting to unlock the extreme difficulty setting.
Healing falling teammates
If one of your teammates falls to the ground, throw a smoke grenade near him. Then, get your health packet out and heal him.
Stealth
On the 4th level, after you drive up to the mines and get out, be Foley, and go up the little ledge. Command your men to stay back. Then, just take out all of the guys you can see. Foley has a silenced sniper rifle on this level so they won't notice you unless they see you. Try to make all of your shots head shots or upper torso shots. You'll know when you've killed every guy in that area because it will say "Objective Completed."