What is the least useful and/or or least frequently used blade in a swiss army knife?

My nominations:

- Phillips screwdriver. The end of the can-opener will work for larger phillips screws. Any screw too small for the can-opener is also usually too small for the big clunky phillips driver as well, making it almost completely redundant.
- That hook-like thing. You know what I mean.

Yeah I was gonna say the hook-like thing too. Also, don't forget the nail file. It's completely worthless.

But doesn't the end of the nail file serve as yet another screwdriver? On a larger knife that already has at least two screwdrivers (on the bottle and can openers) it probably isn't worth much, but on the little keychain knives it will be the only screwdriver you have.

Yes, (at least) on the small knives the tip of the file is a screwdriver. What I meant was the actual file part though, not the screwdriver part...i.e. that blade would be just as useful if it were just a screwdriver and not a screwdriver/file.

"The hook-like thing" is by default the most useless blade on a Swiss Army knife, because it has no present-day purpose. It's a package hook, designed to hook the string on a package tied up with heavy twine so the string doesn't cut into your fingers, and it has no other function. It's useless today because nobody ties packages with twine anymore, but when and where the Swiss Army knife was first developed it was invaluable. I'm sure somebody somewhere gets some use out of them, but they're mainly still included for nostalgic purposes only.

You, sir, deserve some kind of award for explaining that seemingly purpose-free gadget.