Fishing line and hooks, small compass, needles and quality thread, some paracord and leather thongs, a small pair of pliers, a mirror, a magnifying glass, some tweezers, some plasters, the necessaries to make a hot drink, camping can opener (try and get a couple of the US p38 ones from ebay, they'll be the best investment you ever make), small metal spoon, a whistle, some pain killers, matches, a candle, a condom (for water), water purifying tablets, cotton wool for tinder, duct tape, a disposable razor, some razor blades, brass picture wire, safety pins, some alcohol wipes, soap, chocolate.
The list could be much longer, but these are some of the basic ideas. Where are you going to store it, and how big do you want it to be?