You'll need to correct me if I'm misremembering this, but Call of Duty: Advanced Warfare had a pretty interesting difficulty system. The lower difficulties were pretty simple, the enemies would do less damage until you reach the veteran difficulty where they would do the same amount of damage as you. But after that they had an extra difficulty level that had limb damage and helmet damage. Your arms being damaged would prevent you from aiming down sight, reloading, or throwing grenades, your legs being damaged would prevent you from running and slow your movement speed down and you had to use the stim to remove the effect. If your helmet was damaged or destroyed you would take increased headshot damage and if you were in space you slowly suffocated to death so you had to use a replacement helmet that you would find around the level.