Great lists from Jandismo and Lisa. A good guideline.
I am going kayaking/camping this weekend. First on my list is a first aid kit. Make your own.
Mine has an ace bandage, alcohol pads and hand sanitizers, "new skin" for blisters, triple antibiotic ointment, butterfly bandages, waterproof band aides, benadryl spray, eye drops, a small CPR kit, gauze tape that sticks to itself, hydrogen peroxide, aspirin or pain relievers, etc..
I wouldn't count on a store bought first aid kit to have what you might need.
My friends and daughter's friends are old enough to know better, but we still get boo-boos!