I also carry a bag of misc bolts and nuts from the different modifications where I got new hardware from the manufacture, I throw the old stuff into this bag or 1 or 2 of them.
I also have a small box with wire repair tools, splices, wire, and this box has my spare fuses and a couple of switches.
They have come in handy to help people if they have broken a bolt or had one come loose and fallen out.
I also have some two part epoxy that can be mixed up to slow or stop a radiator leak. It is supposed to be strong enough to hold pressure like on a steering line or a radiator coolant line.