On a more serious note, I carry:
PARTS:
Belt, CPS, RCM, headlight bulb, tail light bulb, turn signal bulb, numerous spare fuses (not just the spares in the fuse box), one quart of oil, tire plug kit, air compressor.

TOOLS:
My basic kit: Bosch 1100 code reader (the CP123 series is better), nine screwdrivers (philips, flat, torx) small 1/4" metric socket set, 1/4" ratchet extensions, small External torx socket set (1/4" drive), larger external socket set (3/8" drive) ratchet for each socket set, wire strippers, wire cutters, multimeter, several long clip leads, "kitchen tool set" (has two adjustable wrenches, small vice grips, needle nose and conventional pliers, punch, file, magnifying glass), paper towels, detail towels, detail spray, 91% alcohol, insect repellant, sunscreen --- and other items I cant think of.