Reliable self defense devices include pepper spray and stun guns. The SABRE RED police-strength pepper spray and the Terminator 15 million-volt stun gun are reliable options in each device category, as of 2016. Laws on self defense devices vary depending on the area, so users should check the legality of any device prior to purchasing it.
Pepper spray is a self defense option that the user can spray at an aggressor from a distance. It doesn't require much training or strength to use, and it's a non-lethal method of self defense. The effects of the spray last for over 20 minutes; however, pepper spray doesn't work as well in windy weather, and using it in close quarters is sometimes difficult.
Stun guns shock the aggressor, causing both pain and involuntary muscle contractions. They don't work as well from a distance but tend to be better than pepper spray for close quarters defense, as they work on any part of the body. The effects of stun guns are brief, so the user must get away quickly. Stun guns also require batteries or a charge.
Both pepper spray and stun guns are inexpensive. One self defense option is to purchase both so that the user is prepared for different types of situations.