I carry a 3 1/2" fixed pocket knife.
When it comes down to it, any "cutting edge" or "fine point" object will do damage when it comes into contact with human skin. even the most dull edged knife can make a great shank.
But instead of just carrying any old pocket knife, I make sure its NOT made of stainless steel, as that shit will snap in extreme conditions. Second I make sure its a thick ass piece of either carbon, or carbon reinforced if you have to go the cheap way out. By thick I mean the blade edge should be as thick as the dull edge. Dont sit there and say they dont have stuff like that, cuz they do. Its called antique stores. SOME antique stores.
Also I carry a large oak walking stick. As well as a shorter oak mace i carved. Not the "spray mace", but an actual Mace.
The walking stick I call "spinesplitter" bc it has been used and it does do somethin akin to that. As for the shorter mace, Ive used it a few times, and let me tell you, do NOT understimate finely shaped wooden points. They penetrate deeply.
Other easy to conceal easy to use weapons include
Blowdarts (Unexpected and put you down fast)
Bricks (no sane person will come at you while your holding a brick. bc if they get within certain distances, most are well aware you can also throw it, and id rather not be hit in the face or anywhere with a brick)
Bola (easy to use, even in close quarters, and they trip up and trap up the enemy, leaving them momentarily or permanently helpless depending upon the persons IQ)