In general, you can and should engage in any kind of martial arts, you can first of all for yourself to cultivate willpower, preferably Ashihara Karate, Kyokushin Karate.
The closest thing to street self-defense is the system of national Jewish massacre - Krav Maga. I didn’t practice, but the descriptions of the principles look convincing and realistic, the emphasis is on the application on the street.
And so, of course, you need to keep track of the situation (do not enter the entrance with suspicious strong guys), do not run up (do not dwell on hail), if possible - break contact with the aggressor (get out at the first opportunity) and connect an external resource (police).
Practice a few effective techniques, so that at the level of reflexes. Put the blow. Well, wear a can, preferably an inkjet one. Get it out quickly, too.
There is no better karate than in pockets on TT ...
But seriously, if we ignore the demagoguery about the fact that a criminal carefully chooses a victim, a crowd of youngsters with bricks will beat the master of sports and the like (which is true, of course, but what does it have to do with it), then there are not so many options, and the simplest and most effective of them is boxing. Boxing involves the application of the most powerful, simple and quick blow to the head (preferably), which in a one-on-one (and even one against two) duel practically guarantees victory / saved phone / honor / life. Another question is that boxing training is exhausting, requires a good trainer and is quite traumatic.
The main reason street robberies are successful is the surprise or outnumbering of the attackers.
The victim is either unexpectedly beaten from behind, or otherwise deprived of the ability to resist. One c / c told me that the three of them went to work. they chose a deserted place, caught up. If a person did not have time to turn around, just from acceleration, two pushed him to the ground, and the third pressed him down from above. A person in such a situation receives a lot of strong blows before he has time to understand something.
And if suddenly a person managed to turn around and prepare for defense, then one criminal immediately hung in his arms, the other threw himself at his feet , and the third tried to go in from behind again.
The street does not imply any fair fight. Self-defense skill (it is not so important which one, the main thing is that there is a habit of full contact) can help brush aside a drunk who is looking for a "fight", or emerge victorious from a conflict that has a reason and begins with words and quarrels. And where people who think calmly, initially simply have the task of knocking down and robbing - it won't help much, just won't have time.
I had a friend, an army sergeant. Healthy as a moose and strong as a bear. Boxing and barbell replaced his women and career.
So he was beaten and robbed on the street by four 17-year-olds. Simply because there were more of them and they attacked suddenly - they immediately kicked something over the head and simply knocked out the man, before he had time to raise his hand. And no amount of strength and experience helped.
Can I quote an anecdote? "Run."
Funny or not, but the reality is. Most street crimes are committed with intent - i.e. a potential perpetrator is not only ready to attack, but also carefully chooses a victim. The victim, not expecting anything like this, falls into a stupor. You can be a world champion in karate, but that will not save you from being hit in the back of the head with all the consequences. My own brother was the victim of such an attack - he spoke on the phone - a blow - an ambulance. He does not remember what happened between the ambulance and the strike (which is almost 4 hours).
Be careful and try not to intersect with large and clearly aggressive groups of people. Rimbaud only appears in films.
And yes, do whatever sport you like.