My former self defense guru advised carrying aquarium gravel in your jacket's outer pocket so that you can fling it into an attacker's eyes to set up a hit, kick and the like. The idea is an old one, the old throw sand in the eyes trick, perhaps first invented by the Egyptians. When I lived in an urban area with a high volume of crime I used to carry aquarium gravel in my outer pocket, but thankfully, no one ever attacked me. Still, I think it is a good one, temporaily blind your opponent even for a moment can make the difference between victory and defeat in an emergency self defense situation. And it is legal. Aquarium gravel was advised because it is clean, any gravel will do. The only draw back was it was a pain to have to clean out of your pocket when it was time to wash your jacket...