I carry a scaled down version of tools you would find in a typical garage. dont forget a decent jack/wrench, electrical parts (wire nuts, strippers, tape..) WD-40, hammer, flashlight, screwdriver set, small tube of silicone, sockets/wrenches,pliers, zip ties, multi-meter, etc. there is just a lot of stuff you CAN carry, just need to figure what you NEED to carry. no need to add addl weight to your rig if you dont need to.
*Currently trailer-less but shopping
07' GMC Envoy w/ P2 controller (current TV)
88' Chevy K5 Blazer (soon-to-be TV)
74' VW Superbeetle (1303)