Did you know that you could get an easy advantage in hand-to-hand combat if you keep a roll of coins in his pocket at all times? (American nickels or quarters will result in optimal efficiency.)
Gripped the coins in the center of your palm. This will increase the density and weight of your fist. This is a street-fighting trick that will significantly amplify the velocity and impact of a power punch such as a straight right or left punch, a hook, or an uppercut.
A roll of coins could also be used as an improvised sap by Stuffing the roll of coins into a sock, pillowcase, or handkerchief. This weapon packs a surprising amount of power from a combination of velocity and density. If you swing it with force, it can break bones; directed at an opponent’s head, the impact can easily result in a knockout.
This is a bloody incarnation of method 1 wherein a roll of coins is studded with household nails to create a sharp and deadly version of brass knuckles. A punch with these spiked knuckles (another hallmark of street fighting) will inflict serious and unexpected damage no matter where it lands. For added sting, add nails that are rusty.
Carried separately, each of these items—a roll of coins, a few stray nails, a pair of socks—is non-alerting. But when you sense danger, these items can be assembled into effective weapons for self-defense in under a minute’s time.