Face it, no matter how many YouTube videos you watch on the subject, trying to disarm a gun-toting attacker is probably going to get you shot. Thus, I suggest an alternative course of action -- a biomimetic self defense strategy patterned after the armored ground crickets (Acanthoplus discoidalis) of Southern Africa.
Step 1: Cover yourself with spikes
With an exoskeleton covered in sharp spines, these crickets aren't exactly cuddly. Anything wishing to make a feast of their innards is going to need to exercise a little caution. As such, consider adding more punk attire to your daily wardrobe choices -- maybe even some spiked shoulder pads like the Road Warriors wore to the ring. Potential attackers will instantly have to think twice about approaching you.
Step 2: Strengthen your jaw muscles
If it works for the armored ground cricket it might work for you: Be prepared to bite the bejesus out anyone who comes close to you. This not only means keeping a healthy set of chompers, but also exercising the jaw muscles. There's a lot of discussion in mixed martial arts circles regarding exact methods, as well as overall effectiveness, but some recommended techniques include chewing gum, hard nuts or even bits of foam or rubber. I'm not sure how some of that helps dental hygiene, though.
Step 3: Rub your arms together to make noise
Like many insects, the armored ground cricket rubs its limbs together really fast to make a loud, threatening noise -- a practice called stridulation. For humans, rigorous limb rubbing doesn't do much unless you're wearing nylon or polyester. But you can do better! Consider strapping slate to your right forearm and chalk to your left.
Step 4: Vomit absolutely everywhere
For armored ground crickets, this step helps deter attacking predators from eating them. Might a potential mugger might think twice of continuing if you got sick over everything? It's worth a try, right? Be warned, however: According to a recent article at BBC News, scientists have found that vomiting doesn't work near as well as the next cricket defense strategy.
Step 5: Hemorrhage blood like crazy
The armored ground cricket's last big hurrah is quite sensational: It hemorrhages its foul blood through cracks in its exoskeleton, coating itself and its attacker in slick, green gore. In an experiment pitting lizards against crickets, a team of researchers found that while all their "clean" crickets wound up in the belly of a reptile, the ones covered in blood were often left alive. Granted, you're at a bit of a disadvantage on this one. You have blood in a closed circulatory system, while insects have haemolymph, an open circulatory system fluid that fills their entire little bodies. So it's a little easier for them to squirt gore, and it's nasty, foul tasting stuff. That being said, if you can manage to go all Clive Barker on your assailant and turn into a sanguine yard sprinkler, there's a good chance the attacker will freak out and leave you in peace. Also, you might want to call a hospital at that point.
Unlike most humans, however, crickets aren't above a little cannibalism from time to time, so coating themselves in haemolymph can actually make themselves an even more attractive meal to their own kind.
So, if you choose to use the armored ground cricket self-defense system, be very careful. If you coat yourself in blood, clean up quickly afterwards and try to stay away from strange men with sharp teeth.