Actually the safety points that have been made when meeting ANYONE from the internet for the first time.
Knives though, really?
A big wad of keys to stick between your knuckles or a roll of quarters to weight your fist is probably better, legal, and you always have change for the soda machine.
Or, back in the 70s gangs would carry bottle openers. The ones with the pointy end for punching through the top of a tin can. You can sharpen one on the sidewalk and a good rake with it will cut straight to the bone.