People tend to refer to a stun gun as a taser and they are NOT the same thing. It is important to note the difference as there are specific laws set forth that pertain to either stun guns or tasers.
Stun Guns you have to have direct contact with the stun gun to the person. It is a high voltage tool to quickly immobilize the attacker. It transfers the energy to the muscles of a person at a high pulse rate. As a general rule, a one-half second contact will repel and startle the attacker, they will feel some pain and muscle contraction. Thus the attacker will let go and you can take off and get out of there. One to two seconds contact can cause muscle spasms and a dazed metal state. The best place on a person to target with a stun gun is the large muscle groups - abdomen, groin, thigh, back, etc.
The energy will not transfer from person to person so even if the perpetrator has a hold on you - you will not feel it.
If your choice of self defense tool is a stun gun then you need to get over the fear of the electricity that comes out of it. The strength of the energy of the stun guns are not considered lethal. Also, you need to find one that will suit you and your personal situation. Does it fit your hand, easy to handle, etc.
The taser you do not have to have direct contact with the device to the person. The taser deploys insulated conductive wires with a maximum length of 15 feet. The BOLT transmits electrical pulses along the wires and into the body affecting the sensory and motor functions of the peripheral nervous system. It is not dependent on pain and is effective on subjects with a high level of pain tolerance. Persons with a very high tolerance to pain (e.g. drug abuser or a trained, focused fighter) may be able to fight through the pain of a tradition stun gun.
Taser technology is designed to cause incapacitation and involuntary muscle contractions, making secondary injuries a possibility. There is a difference between what the general public can use and what a police officer can use. The police taser is much stronger and have more projectiles, have further range and also shoot at a higher rate of speed. As a civilian, this cannot be legally owned without the proper training.
Which ever you decide to go with you need to check your state and local laws as their may be specific laws set forth for both.
The link below is where I have obtained some of my information and they also have a great list of Pros and Cons which I encourage everyone to go read before you decide on your choice of self defense tool.
Another website I have used for information is as follows: