Some knives are trouble, other knives are tools.
I always carry a swiss army knife with a small blade, nail file, scissors, bottle opener, can opener, screwdriver and a few other functions. There are times when it is really handy.
I was once on a beach in Mexico with some friends and bottles of cold beer and limes. I was the only one with a bottle opener and knife to slice the limes. I was the hero of the moment.
If I had to use it in a fight I wouldn't try to use the blade, I would just hold the unopened knife in my fist to make the punch land a little harder. However I have never needed to do that and probably never will.