I bought a $3 mini hook knife for my keychain off Aliexpress. I was tired of getting my pocket knife or Leatherman confiscated or stolen “for security reasons” at ever increasing (and surprising, like libraries, bars) venues. The majority of my needs was to cut open boxes and plastic packaging anyway. It’s the size of half a stick of gum, pops open with a button, and only the inside of the hook is sharp, making it pretty safe for wet hands. The handle is part carabiner clip. Not sure how long they last, since they get confiscated, but at $3 each, I don’t care. Keep it on my keys. The clip makes it easy to take off my keys if I need to leave it behind, but if I end up getting it stolen, meh.
It cuts through cardboard really well, and also opens that hard plastic packaging, burlap sacks, plastic strapping, and that weird material large dry dog food comes in.