I strap a militaey style MOLLE medical pack to my rear seat. Holt wrenches, tube repair, fixaflat can, screwdrivers, spare fuel hose, headlamp, zip ties, allen set, a spark plug or two. If i go on a long trip i wear a small backpack with a hydration pack with some other tools.
I never thought about the headlight, not a bad idea.
IDK man, mine is pretty minimal. I do all my own repairs and service for a reason, so I know when something is iffy or about to go bad and I plan accordingly. Beyond that I just keep stuff for slight tweaks and the such as the need hits me. I guess you can't always look at something and know if it's going to go bad, but doing all your own service should give you an idea. Come to think of it, I think I'm going to start packing the following: Spare headlamp, spare fuses (kinda goes without saying), inner tubes, tire spoons, a 12 and a 14, my pliars / multi tool, allen key set, and a multi screwdriver. Maybe an extra coil. That should pretty much do for anything surprising.
