Kennesaw, Georgia, passed an ordinance in 1982 requiring each head of household to "own and maintain" a gun. In the subsequent 25 years, there have been zero fatal shootings in Kennesaw, and Kennesaw's per-capita overall crime rate is less than half what it was in 1982 — despite Kennesaw's population having grown by a factor of five to one.
Kennesaw's mandatory-gun law was passed (unanimously) in response to the total handgun ban passed by Morton Grove, Illinois. Morton Grove's crime rate increased by 15.7% following the ban, while the surrounding Cook County's crime rate rose only 3%.