I really enjoy this thread. Let me give you some background info about my situation here.
I live in Berlin, the capital city of Germany. I live in the inner city, not a bad neighbourhood per se, but there are mostly arabic/turkish people here, and cultural differences often lead to conflict. I don't own a car, I get where I need to get by bike/skateboard/public transportation. I can't legally carry a gun. I do carry a knife most of the time. I don't see knives as defensive weapons, but they do have some impact as a visual deterrent. I also always carry a strong flashlight, and sometimes some pepper gel.
Maethor,
I'm glad to hear you've gotten through those hairy situations well and safe. All in all, the best advice that I can think of is this:Know the areas you travel within very well, get to know people there, especially the police and shopkeepers. Know the normal sights, sounds, and faces. If something seems out of sorts, or you just get a bad feeling--split. Also, you being six foot, one-eighty, that's not a bad weight class. You'll likely have more than the average reach by both hand and foot, and if you practice a martial-art, that
can make a difference with that. Adding in, if you have the time for it, a basic regime of weight-lifting and cardio can also go a long way. I'm often pressed for time, but I still manage to get in a good workout in about thirty minutes. My workout is detailed below.
Military-Pressing (75% max weight, 12 reps by 2 sets)
Chest-Pressing (75% max weight, 12 reps by 2 sets)
Squats (75% max weight, 12 reps by 2 sets)
Upright/Bentover Rowing (75% max weight, 12 reps by 2 sets)
Pushups (Or Pressups) 75 in a set, 2 sets
Situps 75 in a set, 2 sets
That takes me around thirty-to-forty five minutes, and then I allow myself to cool down by studying my most well-trained and used survival skills. After that a thirty minute self-defense routine. (I've trained for over seventeen years now.) Krav Maga, from what I can remember, requires a partner to be the most effective in practice, but from what I have seen it's quite effective.
You made quite a few good points there. I tend to be broad-shouldered and cold looking (Can't help it lol). But it does seem to make people think twice. My wife and I often take our dogs walking, and even if it is COOOOOLD out I don't wear anything bulky. Unless I have to, I don't wear a jacket. Predators will often look for slow or weak prey (yes, just like predatory animals), especially those that are ill. A target whom is muscular and looks as if it would give them a hell of a resistance, are often avoided. Also, though, those whose face is difficult to see, will often draw the attention of law and authority. Watching one's surroundings is often one's best defense.

Stay safe!! You sound as if you have had quite a bit of experience.