What a lot of other people have said...
Duct tape wrapped around an old gift/credit card.
Fire making capabilities, even if you don't smoke.
Small note pad/book.
Minor first aid. Alcohol wipes, bandages, pain reliever, maybe ant-acid and allergy pills. (depends on your needs)
Extra battery for your flashlight.
Super glue
...and of course a Swiss Army Knife that fits your needs.
It is a tiny tool chest in your pocket.