I have a tiny, bladeless (so okay with TSA for flying) "pliers"-style multitool that fits on my keychain. I don't think that the manufacturer makes it any more. Searching for "keychain multitool" will turn up various designs on Amazon.

I also have a separate tiny folding knife

I think a Spyderco Bug, though any tiny knife is gonna be equivalent, and I'm sure that there are more-reasonably-priced tiny knives out there

that fits on my keychain that I take off when I fly.

For infrequently-used tools, those are large enough to be fine for most things, and it's less of a pain for me to haul around than a full-sized multitool or knife (which I have, in the past, carried).

I don't know if I'd say that it's a game-changer for me, but it is convenient to always have said tools at hand.