These inspired the list. They are amazing, are commonly included in high end med kits, and I don't know why most kits don't have them. While they are most commonly used as a temporary cast or brace, they are flexible and handy in a pinch. Pick a size that suits your needs and space.

Put a week's worth of dramamine in your go bag, it can turn a bad day good, and save a trip. Stick to a low dose to avoid drowsiness.

While this is not for your go bag, this is great to keep in the bathroom cabinet at home, as an affordable, effective disinfectant.

This is a perk, not a must, but is used so commonly that I don't see a reason not to include it in practically all first aid kits. I use it most for cuts and scrapes on the hand, and other places where a bandage would be awkward.

First aid for kids can be a little different, and this is doubly true for babies. Give it a quick read before you need it if possible.

Let's face it, your dog is more likely to eat or do something dangerous than you are, and it can be much harder to get medical care for a pet quickly. (There are a variety of these books for different types of animals.)

The Merck Manual is one of the classics. It is understandable, covers all kinds of medical topics, and designed for the average person to be able to follow it. This does have a section on first aid, so if you don't have one of the quick reference first aid books with your bag, pack it.

If you are likely to end up leading a camping group, or want to learn more than cpr, this is interesting.

A swiss knife includes tools that you otherwise may not have, such as basic tweezers. It can be amazingly handy for people leading a camping group. If you'd like to splurge, choose a multitool with a magnifying glass, to make tackling splinters, ticks and stingers easy. (Note, if you get a med kit with forceps, never mind the tweezers.)

If your kit is designed for camping, emergency preparedness, or anyplace you might not have clean water, being prepared for water treatment is very important. (You probably also want to bring your favorite hand sanitizer.)

If you react badly to insect bites, or are heading out where you're likely to be bitten by something dangerous, this may be worth considering. I would consult with local experts on their recommendations of likeliness of dangerous bites, and best treatments.

This is roughly twice the size of the basic kit. Opening a dry bag will cost you a few extra seconds, so if weatherproofing isn't required, consider a rothco bag instead. If having a dry bag is vital, this is a good choice.