The one thing I always carry is a tube of antibiotic ointment. It has helped avoid scars and trouble in many instances, and not just for me. I generally wash a cut/ minor road rash with water from my bottle and spread the ointment on. I also have a couple of band aids, too, which I have used on occasion.
On our first tour, we were crossing a main street in Austria, as the cycling path crossed over to the other side of the street. I am not very good at hard right turns, and instead of unclipping and dabbing my foot down, to get up the curb cut, I turned my wheel too much and ended up rolling right down a pretty steep ravine, into woods full of brambles. Since I had brought my own saddle bag to put on the rental bike, I just took out my little tube, spread it on my leg, and, I was off. The leaders never even knew what had happened, until I told them.