[Milkshake]

It depends on what the field has to offer, but I always take chairs, and if possible my canopy. Learned that lesson the hard way, went to a field new to me and there was no shade at all, August here in south carolina can put a hurting on you if you have to sit in the sun alot. i was so miserable, went the next day and bought a 12'x12', and take it whenever possible. Better to have something you do not need than to need something you do not have.
I bought a crap load of o-rings for tanks, always someone who needs one (or a battery), I put 10 in a bag and sell em for a buck, good deal ?
I always change out my batteries and check them ($2 9v tester is handy) keep the good used ones to give to the newbs who never show up with supplies. Better than throwing them out in my mind. I always tell them they should bring extra, but you know how that goes.
I liked the socks idea, I keep a pair in my glovebox, along with a pair of undies, never know, some of those field "squirt dogs" mike hit you at the wrong time and oops.
Food- I take p/b crackers and viennas with me, easy to eat and pack.
Hydrate- any type of gatorade or other brand is great to take, replentish the old bodily fluids.
Most important thing- friends to shoot!