Being a nurse and all, what do you think should be included in a first aid kit? I would like to put one together for my wife and myself, to carry in our car. We are both average folks with a basic working knowledge of First Aid. I just believe in being over prepared and hoping we'll never need this stuff. Also, given our situation, it might be preferable to buy a kit rather than put one together ourselves.
The most important thing is not in any kit. That thing is knowledge and the willingness to use it.
My own kit consists on various gauze sponges, 4 inch silk tape, a couple of oral airways, some cord, a 12 inch piece of broomstick, a CPR mask, a pamper, a pair of "cut anything" scissors, a couple of opsites, a bottle of NTG, and an analphylactic kit containing epi, benadryl, and decadron as well as a couple of syringes. My "kit" is kept in a ammo box in the back of the car.
If you can only chose one thing though, choose knowledge, and supplement that with a creative mind that can improvise under pressure.