Keep a couple spare doses of your meds.

You never know when you will desperately need to be able to start a fire. Firesteel is one of the more fool-proof methods, assuming you have basic fire-building skills. This unit is perfectly sized for a keychain.

Maybe you prefer a swiss army knife -- but I've recently become a Leatherman convert. Squirt comes in a scissors model, too, but with a blade already on the Squirt, I think pliers are more useful.

Keep all your important files with you -- including medical records.

Clip your keychain to this to keep it secure in your pocket. I like to keep items on separate rings around a central ring.