Buffalohump and anyone else who is not trained in advanced first aid, in all honesty forget the first aid kits in the sense of store bought ones and what you need,
for right now. It would be far more useful to get at least certified in firstresponder training or its wilderness equivalent.
Being able to know what to do and how to do it will be a lot more useful then a store bought first aid kit. And once you have become trained you will know what needs to be in your kit! I think this apples to every one who goes out into the wilderness, as they say about bushcraft the more you know the less you carry.
I got my redcross cpr and basic first aid when i was 12 and 15, then at 16 or 17 i got my firstresponder cert, and retook the course again at 20, and now having just finished my EMT class at 22, and am going for that cert.
Store bought First aid kits are good but they really dont help in so many situations were knowledge is more important, but i cant tell you how many times i have heard people say and even my friends "i heard some one calling for help, i rushed over to help" Then i say "great what did you do" them " i got there and asked what was wrong, then i um did not know how to help, and stood there" This happened to a friend of mine, and after that they realized they had no idea about how to help really, so they took a class on crp/basic first aid. Now they can help and be useful! And the person is very proud of them self, and may be taking the next step up.
My first aid kit includes firstresponder training, cloth tape!, triangle bandage!, gaze pads/rolls and tinfoil/emergency blanket, and plenty of the woman "products" there great for soaking up blood!. Those items alone can do about everything you need as far as healing your self from cuts and broken bones and wounds. For providing rigid support use branches or sam splints if your traveling alone, as i think it would not be fun whittling splints with a broken arm! And some cloth tape and gaze rolls, and Triangle Bandage, in case i forgot those.
For splinters and personal grooming, sewing pins(for splinters i find it easyer to dig them out with needles/pins) and nail clippers. Along with sunscreen and sunglasses and a form of an after sunburn cream/gel. And a good old fashion bar of soap.
For meds anti diarrhea, anti itch/bug bite, and pain killers. Also make sure your caught up on all your shots like tetanus. And if you can get some anti antibiotics, and advanced pain meds, legally of course. This will help in case you are stuck out for a time you will be able to feel, better long.
Though i will say knowing more about first aid makes you want to bring more, like do i need the air tank, body brace, neck brace, oral tubes, bp cuffs in infant and over sized, femur traction torture device, soon you have more medical crap then you do "hiking stuff". So just forget my post haha
ps a sterile water sqeeze bottle is great, the one with the "hard straw" bent at an L. Washing wounds and eyes.