Photo shoots for me tend to be situational where each situation demands specific equipment. As a result I am constantly playing this ' what do I need this time ' game and end up sorting through the gear to determine what I really and/or might need vs what is just extra weight. Over the years I've managed to refine the process into an art form and can pretty well get the selections right for most any situation, but I still tend to carry more gear than I need to. Of all the gear inside the bag, only one piece is carried for every outing...the camera, my Sony A65 which has performed very well for me since I first acquired it some years ago now. Everything else is optional.
Take for instance when I manage to shoot Oklahoma's Tallgrass Prairie. I really do not need to carry five speedlights or a bunch of gels, nor do I need the electronic triggers for those lights, so they tend to be left behind. The slots they use are better filled with a few extra water bottles as I will be hiking across rough terrain on what at times can be very warm days. When hiking across this landscape I will often find myself some distance from my vehicle, so I need to be prepared for just about any kind of weather. Rain gear is a must and so is a rain cover for the camera and bag along with a light weight cotton scarf which is useful for many things. Shooting the Prairie requires multiple approaches, so I will carry my 18mm to 50mm f/2.8 lens along with my 50mm to 500mm zoom lens. This combination gives me a great range of shooting options. I will also make sure I have with me a graduated neutral density filter to help with balancing the exposures between the sky and landscape.
When I am on a location shoot with a model or for a concept photo shoot the contents of the bag changes. Speedlights become essential equipment so I will carry all of them along with triggering devices and mounting attachments. In addition to these, I will carry again the 18 to 50 lens along with the 50 to 500 lens. Although I tend to settle in using one lens, I carry both just so I will have them if I need to switch. This also requires stands for the lights and a softbox or two along with sandbags to anchor the stands against the wind. These of course are carried external of the camera bag, but are essential accessories for these kinds of shoots.
Shooting at night requires a different setup depending on what you are doing. A concept shoot at night uses much the same equipment as I would during a day shoot with more emphasis placed on the lighting equipment. The same applies to a night model shoot. Shooting the night sky requires very little equipment. A tripod and camera, remote release, and a wide angle lens is all you need so I rarely even carry my camera bag when making this kind of shoot. Most of the time I simply transfer the few extras to a smaller hand carried bag and keep it simple.
The camera pack also has a variety of zippered compartments where I carry things like cleaning cloths and solutions, extra batteries, a few bandaid's, writing material for notes, remote releases, and various cables and connectors along with other obscure and rarely used accessories. There is also a place for a laptop, but I rarely ever carry one.
Over the years the Tamrac Cyber Pack bag has become an essential part of my photographic efforts and I have put it to hard use. It's wide shoulder straps allow for cross country treks. A single, well designed handle across the top makes for easy transport from and to a vehicle. The myriad of adjustable pockets and zippered pouches allow for just about anything to be carried inside. The large solidly built zipper has held up well with constant opening and closing. A series of straps allows for things like a tripod to be attached. It's rugged construction has held up to aggressive use for close to a decade now. It has contributed as much to the success of my photography efforts as any piece of equipment I possess. Certainly, it is not your ordinary camera bag.