I have a couple of John Hedgecoe's books. The sample kit included in one of them is absolutely ridiculously packed: checklist, tripod, tripod screw, grey card, notepad, table tripod, cable release, instruction manuals, screwdriver, stapler (??) adhesive tape, modeling clay, scissors, pins, meter battery, clamp, film, meter, camera, flash, hoods, four lenses and included cases. I've used a number of these on location shoots, but they don't come with me most days.
Obviously it depends on what you like shooting, but for me as a street shooter:
M body, 35/50/90 lenses, a couple rolls each of 100, 400 and maybe high-speed film. Maybe a flash or X100 if I think I'll be out after dark.
The tripod and cable release only go if I intend to do night architectural photography.