I carry 5 lighter flints Krazy-glued to a small key blank and secured in place with a clear plastic piece of shrink tubing. It's possible that it might be confiscated, but so far no airport security person has ever given it a second glance. If they ever do - well, I paid less than $2 for the components and could probably do it cheaper next time.

I also have a key fob with a stainless steel "logo" attachment that will strike a spark from said lighter flints.

In my wallet I have a first aid certificate with a cotton ball laminated to the back of it. You can easily make luggage tags out of business cards the same way. Even if I don't have a knife to cut it open, I'll bet I can punch a hole through it with my car key and rip it apart. Because it's laminated, it will even keep the tinder dry if I go for a swim.

I also have a Princeton Tec LED light and a mini CPR one-way valve (for first aid rescue breathing) on the same keychain.

And of course, the obligatory Fresnel credit-card lens. <img src="/images/graemlins/laugh.gif" alt="" />