I'm as bad a gear-head as any photographer I know, but for my day-to-day work, I have my equipment distilled down to essential pieces. I may add a lens or two for certain assignments but the cameras and lenses in my Domke bags are there for good.
The trunk of my car has just enough room for the following bags: a small Domke pouch that holds my Digital Camera Battery, 4 Pocket Wizard Plus units and associated cables, a Nikon SB 26 flash and a small tabletop tripod; a Domke F2 ballistic that gets stuffed with 1 Nikon D3, 50 1.4G, 85 1.4, 24-70, 70-200, a Think Tank Pixel pocket with 4gb Sandisk cards, 5 or 6 batteries for the camera, small led flashlight, SB 800 and t/l cables, leather notebook, small bottle of Tylenol or Ibuprofen, extra pens and Sharpies and a current passport; Domke F 3XB ballistic bag with Mamiya 6 film camera, 50 mm lens, 75 mm lens, lots of Tri X film, some Fuji Acros film, an 8X neutral density filter, cable release, a small Vivitar 2800 flash and a pocket sized Moleskine notebook.
There's also the ThinkTank Shapeshifter backpack which is loaded down with a Macbook Pro, extra extensions cords, a three outlet grounded adapter, 3 card readers, Bell Turbo stick, business cards, laptop locking cable, Zoom H4n recorder, xlr cable and shotgun mike, 14mm wide angle lens , a 24 1.4G lens and a second D3 body.
A couple of things you may have noticed: I only have one D3 in the bag. I used to carry two bodies for all my assignments no matter how big or small. I've since cut things back to just the one body for most assignments in Toronto.
Portraits are a big staple of our assignments and I've come to realize that my back doesn't really need to be carrying two bodies. I've seen friends and colleagues suffer from back pain over the years and I really want to avoid that fate and this is one way to do that.
Of course, on major assignments, I'll be using two digital bodies so there's less lens swapping, but otherwise the D3 has never let me down so I don't worry about total failure at an inopportune time. The only downside to single body shooting is the lens changing which means I may have to blow dust off the sensor a bit more than others.
As for the Mamiya, I almost always carry a film body of one format or another every day. Lately it's been the Mamiya 6, which is a medium format camera that uses 120 film. I find the square format lets me stretch my mind and see things just a little bit differently. When I do use it for an assignment (the Maple Leaf Gardens demolition for example) I'll more often than not process the film at home and scan it on an Epson V700.
Lastly, there's one piece of gear I don't use very often but find it indispensable when I do need it and that's a Joby Gorillapod. It's got articulated legs which have rubberized rings and feet which have tremendous stiction and can wrap around whatever you can find. When a regular clamp won't work, this is the answer.