I know I've used this in the past to describe the supportive actions of members of the Vanu Rangers in the virtual battlefield but today, I was able to truly witness angels on my shoulders.
We raided a house that had a terror cell leader responsible for many attacks and IEDs in the area, here in Iraq. When we did, a lot of shooting happened. We had to move quickly on the house otherwise the identities we were there to apprehend would get away while their accomplices shot at us in an attempt to slow us down - because of this, our security on the ground was lacking. Luckily no US forces were hurt, largely because these guys swooped in and took care of the bad guys for us.
Angels on our Shoulders