Yes, it may come as a surprise, I love keychain knives. What? no surprise?
Okay, yes I am the case peanut guy who downsized even more to the SAK classic. I just find that in my lifestyle as a retired gentleman of leisure in the town of Georgetown Texas, I don't really need much knife. I do a hell of a lot of fishing, but for that my old Buck woodsman does the dirty work of cutting bait and cleaning what is going to go into the frying pan. But for most duties in town, like opening mail, Amazon packages, the little 58mm SAK does what I need, and takes up very little room on the keyring. But to me, its way more than a knife, its scissors, tweezers, flat and Phillips screw driver, and thorn/sticket plucker for my dogs paws. I really don't think a day goes by that I'm not using it for something. It's a little multitool with a very wide window of capability. Its kept company on my keyring by the Fenix flashlight that re[laced the E01.
My other favorite keychain knife is my old Christy knife. I love how the blade locks out in three different lengths, depending on what you need. And the blades are replaceable.