Emergency Lighter
The best part about outdoor products, and innovative deisgns, is when stuff hits the fan -- you will be prepared. Whether that stuff being getting caught outdoors in a freak snow storm in the middle of the Sierras, or when zombies take over the world and everyone is on their own -- you will be prepared.
Step one of being prepared, always have fire. Fire = Life.
That is easy with this little keychain tool; the waterproof pocket lighter. Small enough to fit on your keychain, water tight so even if you go swimming it will work, and reliable enough to work when you need it most. It weighs less than an ounce, so all you gram counters out there will be happy with it.
Take it on a trek, or keep it on your keys. You'll be happy that one time you need it, and it is there.