I agree with Daisy - knives are overrated - a very small one will do just fine. A headlamp will be more useful than a handheld, and it should be small. Since it may not be in constant use, be careful of the batteries you put in it. A light that accepts lithium batteries will be there when you need it, unlike failure prone alkaline batteries.

First Aid Kit. Basically, the contents depend on your training. Get thee to a first aid class! Once you get above the band aid level, you need to be able to stop bleeding, and possibly splint fractures. CPR is a useful skill, but if you need to apply it in a back country situation, you are pretty much done for (except for drowning).

Being able to build a fire/create and conserve heat makes all the difference in an overnight situation. What you will carry will depend on the country into which you are venturing.