Sorry, I didn't hear you. I had my eyes closed.

It's always amused me how in movies, as the SWAT/Navy Seals/commando leader and his team are about to ambush the bad guys, he will flash some vague hand signal to his troops (taps elbow, holds up two fingers and points off to the left, etc). Apparently from this they know that means "Six thugs in the next room with the hostage gagged and tied up to a chair. Two more of them upstairs with Uzis. The short one with the scar over his left eye is holding a detonator device wired to some explosives in the briefcase under the table. Three of us should go around to the northwest corner of the building and execute Plan Delta Charlie, just in case they try to escape out the window."

Here are some of the more arcane hand signals, just in case you lost the training manual.