In the sphere of non-lethal weapons, I want to create something that will make an assailant think twice, but not actually kill them.
One way to achieve this would be to make a blank round to be used in a conventional firearm but with very little propellant on board.
This would also incorporate a plug of heatproof wadding and some form of food substrate for insects.
When the gun is fired, the wadding protects a small package of insects (eg lice, fleas, ticks or small cockroaches) as they are thrown at the body of an attacker.
This would so distract them, via disgust/itching that the person under attack would gain crucial seconds and be able to sprint away to safety.
(This might also be achieved using a can of compressed air and a small reservoir of insects driven by entrainment into the air flow).