The Spyderco Dog Tag appeals to me. You have to ask yourself the question... Do you want to carry mostly a knife on your key chain or some sort of multitool that happens to have a blade on your key chain? I like SAKs but I find the Classic too small, even for the tools. I choose the Leatherman Ps4 Squirt. The blade seldom gets used, but I use the little pliers a lot. But the blade is there if I have nothing else with me and I have used it a time or three.
This to some degree. I don't like the idea of a dedicated knife on my keyring. To me, a knife is a one trick pony with just the single use. But even a little Vic classic has so many different uses. A knife blade that is thin and razor sharp for opening packages and cutting twine or whatever. The SD tip of the nail file works on small and medium Phillips screws and even opens imported beer bottles, scissors for detailed cutting and nail maintenance and light pliers work with care. Even light copper wire cutting if you go all the way back in the scissors jaws near the pivot. Tweezers for a lot of things from splinters to roach clip.
I love the Leatherman squirt, but it's over the line weight wise for keyring duty. More a coin pocket tool. I never imagined I'd have so much use for small pliers until I got old and had senior citizen arthritic fingers.
The older I got, the more I liked multi use items.