Army of Two Tips

Burn... Burn... Ahhahahahaaa
When you're in Iraq, at the Oil Refinery there is an easy way to kill a few foolish enemies. If you shoot the red valves on the pipes at the beginning of the mission a jet of fire will come out for 1-5 seconds

PLEASE NOTE: This stratgey doesn't always work after you use it once in the same mission, including if you die