Martial arts is fairly popular and people who do not practice it professionally do so as either a means of recreation, sports or as a way of life. One does not need to be a professional to fully embrace martial arts.
Throughout the world, there are many martial arts and here are the top ones, the criterion being self-defence.
Krav maga translates to contact sport from Hebrew and is the official martial arts of the Israeli special forces. The entirety of krav maga is focused on self-defence. The problem arises from its popularity, even though that is what brought it to many people. Being so popular, people just label some classes Krav Maga, without actually teaching self-defence, but rather a form of cardio exercise which happens to have punching and kicking.
Regardless, for self-defence purposes, one is best taught krav maga.
If you do not know what to learn, then learn a bit of everything. Mixed martial arts is extremely popular as it allows students to learn a bit of everything, or just specialize in two different forms. The problem this type of learning has is in its teachers. You have to find good clubs with great teachers, especially diverse ones. It is impossible to learn taekwondo from a boxing master. Still, for self-defence purposes, mixed martial arts is a great way of learning various styles you can use to defend yourself.
Jeet Kune Do was developed by Bruce Lee, a famous martial artist and actor, who himself was proficient in Wing Chun. He also learned a lot of other martial arts and then proceeded to create Jeet Kune Do which translates more or less to The Way of the Intercepting Fist.
Any book you read from Bruce Lee himself explains a lot of things regarding fighting and positioning yourself, all backed up by reason. Exceptional Jeet Kune Do dojos usually have great instructors, who are also well-trained and have a deep pool of different martial arts.
Wing Chun is a part of Kung Fu, a style, rather. Its origins are rather blurry but they involve a buddhist nun named Ng Mui who invented a style which can transcend gender and size, and weight, even.
Wing Chun focuses on straight punches, direct hits. Some view it as a form of art, rather than self-defence, yet those who are well-practiced in Wing Chun are said to hit like poles, rather fast and hard. It could be used for self-defence, yet finding a good instructor is paramount.
These are the top martial arts in the world, for self-defence. There certainly are more, but these should do everyone fine, provided they have a good teacher.