"Don't bring a knife to a gunfight," so the saying goes. That's about the only time a knife wouldn't be useful, in my opinion. I would feel absolutely naked without a knife in my pocket (or purse, should it be one of those rare occasions when I'm wearing a dress). You just never know. I've not counted the number of times a day that I've pulled out my pocketknife for one reason or another. I've cut twine, trimmed stems, scraped sills in the barn (pesky birds), opened boxes and feed bags, cut roses, cleaned fingernails, pulled splinters; you name it. My knife is kept clean and sharpened always.
Duct tape is another thing I wouldn't want to be without. I don't keep a roll in my purse, but there's always duct tape in my truck. Sure came in handy when a radiator hose blew in a friend's car. A strip of tape will keep lug nuts from rolling away if a tire needs changing. The tape is right there behind the seat next to a few strands of baling twine.
Twine will keep lumber or replacement storm doors from shifting or flying out of the bed of the truck after a trip to Lowe's. Twine makes a good impromptu goat leash. I use a loop of baling twine to hold the big door to the hen house open during the day. If the wind were to blow it shut and a chicken was in the way...it could be ugly.
Back in the day, when hunting with my father-in-law, he always had a bottle of Four Roses bourbon in his truck. He said it was in case of snake bite. I don't think the whiskey would have done anything for the poison, but he'd go out happy. There are those indispensable things one should never be without.
The chances of my getting into a gunfight are slim to none. In the meantime, I'll keep my knife.