My trailer box is a funny shape, so some of this goes in the car.

Trailer tyre x 2 (you do not then HAVE to stop to get a replacement soon
Spare rudder blades
Spare Mainsail
Spare Spi
Jib (that has not been up the forestay).
Various Mainsail battens
Spare telltails
D12
V12
Epoxy and fast and slow hardner.
Glass Matt
Choppped strand
Micro Ballons
Glass ballons
Gelcoat
Epoxy foam
Baking paper (quick way to get a smooth finish on gel repairs).
Roll of Shockcord (for sale at cheap rates :-))
Spare Mainsheet. Various other bits of rope, Spare Spi halyard
Spare Main halyard
Boxes of spare shakles, ferrels, Rudder pins; Rubber joints
2 cordless drills (usually with all 4 batteries flat)
Drill set
Rolls of Spi tape, bathtub sealent (to fix silicone coated Spi's)
Gaffa/Duck tape
Electrical tape.
Spare blocks
couple of boxes of tools

Soggy rule book.
Couple of odd socks
Tuning and log book

Blue Astma inhaler (If you remember anything, please remember this ); there is also one in my tramp bag, Sailing bag, Ski boot bag and pocket.