Another thing that I always have with me is a spare fuel tank. You may think this is odd, but you would be suprised how much it gets used. I've seen guys fiddle with engines endlessly, only to give up, and the problem ends up being a tank problem...sometime internal, and it's just too hard to get to some tanks and make repairs at the field. If I suspect a fuel tank problem, I'll rubberband the tank to the outside of the airplane and try it...you will find out right away that it is, or is not, a tank giving you the fits. There have also been afternoons that I have continued flying with the external tank...and then make the necessary internal repairs back in the shop. I've also loaned out my extra tank several times to other flyers for this very reason.