With gun control regulations only getting tighter, we need to think of other means of legal defense.
Back in the day there was no guns, and yet a whole lot of wars were fought and won just by the old fashion knives, arrows, spears etc.
While nothing will truly replace the gun, the knife is not to be looked down at . A knife can very likely defend you in a whole lot of shady situations. Even just pulling a blade at a would be attacker is likely to scare the attacker/s off.