My EDC key chain includes a small quark mini AA flashlight, the smallest folding "knife" you can imagine ( spyderco bug, just a tiny bit more than 1" cutting edge) and the world's worst bottle opener:

It has been dremel'ed out of some mini prybar thingy. Not really useful for opening bottles (I didn't get the shape right), but highly useful as pry-thingy and flat screwdriver.

The thing is, those items has repeatedly and consistently gone through TSA screenings, in U.S and Europe. The first 2 or 3 times it was due to neglect on my behalf (I forgot to put them in checked baggage), after which I really didn't bother. Probably too small and unoffensive to be illegal, I guess. Now if the TSA doesn't worry about them then I don't expect anyone else to give me trouble.

The knife is too small to be useful for anything but the lightest possible cutting duties. I wouldn't want to whittle a fuss stick, but it is good enough for many urban tasks. Such as cutting zip ties or opening those clam-shell style plastic that covers many of today's gadgets when you buy them. The scraper/bottle opener thingy is very good for opening letters, card board boxes and the like.