For a kinder, gentler, 21st century military/police force:
A gun that is a combination Taser and Glock with tri-state noise-activated safety. Normally off, the sound of a normal gun being cocked releases the safety on the Taser for 5 minutes, the sound of a gunshot releases the safety on the Glock for 20 minutes. Thus insuring that non-lethal force is only available when the bad guy has lethal force available, and lethal force is only available after the bad guy has already fired once.
Based on the idea that evil is only permissible in response to evil, and even then, is best done quickly.