Practically anything you can get your hands on is a potential weapon. Here are few to name some.
- Rocks, can be thrown, very effective, easy to use, availability a problem at times
- Keys, easy to use, common item, easy to conceal, effective, short range
- Keyboard, easy to use, common in certain areas, not very effective, break easily, has some range, wireless easier to snatch and heavier, possible to strangle with wired ones
- PC power cord, can be used to both strangle and hit, common in certain areas, has some range, needs some practice, easy to conceal
- A car, needs some training, pricey, very effective, if no keys than needs even more training, needs space, needs distance between the enemy to accelerate
- CD, breaks easily, crack the side and it's a cutting weapon, easy to conceal
- Belt, easy to conceal, some range
Obviously it depends a lot about where you are. A computer class would not have cars available and a parking lot probably doesn't that that many power cords lying around.