2/2
Lastly, aikido. MMA has given aikido an unfairly bad reputation. MMA doesn't allow 'small joint manipulation' which is a major part of aikido technique. As with judo, aikido has a 'clean' and 'dirty' side. Clean aikido will take someone off guard and lock them in to a submission position very quickly. Dirty aikido- my personal favourite- dislocates fingers, wrists, elbows, collarbones, knees, hips and ankles and can tear ligaments and tendons. A certain well-executed dirty aikido move can pop the acromio-clavicular (AC) joint in the shoulder, leading the target to serious stabbing pain every time he wipes his ass for six months.
No one martial art system is perfect, and the acolyte should really do six month stints at a variety of them until he finds one (or more) that he likes. You have to be careful though- I did aikido before judo, and my judo teacher got very frustrated when I kept instinctively breaking his grip and countering his grapples.
To someone who's serious about well-rounded self defence, I recommend this stack.
-Boxing, for punch defence, attack depth assessment, and spectacular results against the untrained.
-Kickboxing, for leg defence, takedown defence, and the odd retaliatory kick.
-Judo, for devastating throws and newaza randori (ground grappling) if someone unexpectedly grapples or takes you down.
-Aikido, for elegant defensive techniques with zero lethal potential but massive ability to inflict agonising pain, both acute and chronic.
Other martial arts in which I've dabbled include jeet kune do, savate, kyokushin and wing chun. Savate was pretty cool but my teacher's visa expired and he had to leave. The others are bullshit.
Lastly, let me address the fuckwits hereabouts who simply say "hurr, carry a knife/brass knuckles/gun". Pulling this shit turns a fight into an aggravated assault, assault with a deadly weapon, manslaughter or murder. Your best bet is to do everything you can to avoid a fight. Someone pulls a gun or knife, you back down. No biggie. If someone wants to punch on with you and you pull a weapon, you're basically admitting to being a fucking pussy. The best thing you can do if someone wants to fight you, legally and socially speaking, is to subdue and cripple them, preferably in a way that they remember every time they reach for something for about six months.
If you use a weapon, you WILL get in trouble with the law. The depth of the shit may vary depending on local legislation, but it will be there.
If you pull someone off balance and into a hip throw (ogoshi/ukigoshi, judo), then trap their wrist and rip apart their shoulder joint (sankyo, aikido), they're not going to want to fight after that. Plus you've avoided weapons charges. Win, all round.
Take what you want from all that. But if there's one thing to learn, it's that nobody knows everything, and the wider your knowledge the better.