You are vulnerable, but so is the enemy

Using your Spidey Senses is key. You are vulnerable to grenades and sniper fire to the head when you are on the turret of a vehicle without a driver. Remember, sniper head shots are instant kills. When the enemy drives by in a vehicle, aim for the most unprotected part. The flame thrower and shotgun is god for close combat. Watch the cliffs for enemies. Watch the portals, enemies can appear without warning.