Professionally? Rape prevention taught by my brother's Taekwondo sensei.
My mother and I took classes when my brother was still taking Taekwondo back in 1999. I have no idea why but they kept putting me and my mother against each other and they always called on us to demonstrate the newest move they were teaching us.. and no one wanted to go up against either of us either.. so my Mom and I were always partnered with each other and we made each other better fighters.
Aside from that, I learned to fight from the streets. I fight tooth and nail and whatever object I can get my hands on.. I have never picked a fight, or threw the first punch, and I have always been at a disadvantage where my opponent was concerned, but I have ended more fights than I've been pulled away from and not without trying to spill as much of their blood as possible when doing so or putting them in the hospital. And aside from being pulled away from a fight, which, (I consider a technical loss, even if they were unconscious, because I was pulled away before I could cool off..) was often for my own good as I could be arrested, I have never lost.
The girls left me alone or had to change schools and the guys for the most part, thought I was cool and wanted to be friends, where I would later learn that most liked me and wanted to fuck me from the get go. (To this day, I still don't understand how a dude can go from getting mollywhopped by a girl to wanting to fuck her after..)
I have been extremely lucky in the fact that anyone I have ever fought, has never tried me like that again. (And back then, they took their loss on the chin, so there was no coming back for revenge with a gun, like pussies do today..) Even when my brother came along bragging to the kids that were picking on him, that I would kick their ass if they touched him.. they ended up being the younger siblings of the guys I previously fought and I handled it by talking to them about their siblings picking on my brother..
Nowadays, and as an adult, I obviously don't fight anymore, and am a lot more diplomatic, but I will probably end up taking a self defense course for both fitness and to brush up on what I have forgotten over the years.