4. Boom Operator
As much as this would be a really great name for an explosives expert, the boom operator is the one who hold the microphone. If the grip is the muscle for the camera department, the boom operator is the muscle for the sound department. You almost certainly know what a boom operator looks like, even if you didn't know the name. He is the guy who holds the microphone on the end of a really long pole over the action. You most likely picked up on this from a particularly bad movie where you saw the microphone hilariously drop into frame. As someone who has done the Boom Op job on a set, it is one of the hardest jobs on a filmset. Holding a Boom (microphone) in position for prolonged periods of time can get tiring very quickly but you also must stay completely concentrated at all times. Knowing where the invisible 'edge of frame' is (you can't see a monitor) and making sure you are staying close enough to get the best sound as possible but not too close to ever break that edge. If you do, you have ruined the shot and if that was 'the take' you are going to be the most unpopular guy on set with the director, the actors, the camera men and the hundreds of other people who want to go to lunch. And that is if you are lucky enough to have a sound technician behind you. Lots of times you will also be in charge of the sound levels and quality making the job even more complicated. It is a tough job with little glory but one that is integral to the whole production.