Rubber bands for your wing, get plenty of those. They are only good for so many flights and start getting weak, if fuel residue gets on them they weaken quicker.
You will need something to wipe the residue off your plane after flying.
I use baby wipes, other people use windex (window cleaner) and paper towels.
It wouldn't be a bad idea to have a couple of extra props handy as well.
Of course the appropriate tools for everrything. I have a pair of hemostats in my box and use them quite often.