I ride with the equivalent of everything but the kitchen sink, after my mare severed an artery on trail during a ride a few years ago. I know the chances of that ever happening again are small, but they were pretty small for it to have happened the first time!
In my saddle bags at all times:
Easy boot, 2 rolls of vet wrap, 1 roll of elastikon, 2 diapers, wad of roll cotton, bandana, pair of mosquito hemostats, pair of nitrile gloves, twine, duct tape, multi-use tool, people drugs (tylenol, advil, etc), chapstick, rain poncho, camera, cell phone, granola bars, 2 water bottles, and heartrate monitor.
There is no joy equal to that found on the back of a horse.