What self-defense weapon can a guard carry without needing a permit?

The correct choice is that a guard can carry pepper spray without needing a permit. This self-defense weapon is generally permissible for security personnel to carry in California, as long as it is used appropriately and in accordance with the law. Each of the other options typically requires special permissions or permits due to their classification or potential for misuse.

Batons and electrical stun guns have more stringent regulations regarding their use, which often necessitates specific training and authorization. Handcuffs, while they may be used by security personnel, are not classified as self-defense weapons per se but rather as tools for restraining individuals. Thus, pepper spray stands out as a self-defense weapon that can be carried legally by security personnel without additional permits, making it the correct choice in this context.