If you've ever taken martial arts, you've seen a small finger size wooden stick called a kubotan. There are many tactical uses for a kubotan. One such use is to paralyze your attacker in a fight by hitting them in the clavicle with the kubotan. This will nearly always immobilize their affected arm.
You can however use other tools like a pen, pencil, chopstick or just about anything that can withstand a small impact to penetrate the body. There's now a product called a tactical pen which acts somewhat like a kubotan. Its more sturdy than a pen and built with a durable encasing. One blow from this would stop almost any attacker.