when i was younger, my uncle taught me a lot of bujinkan budo taijutsu (ninpo) and it can really enlighten your awareness and heighten your senses. it's really good in dark alleys or with the element of surprise. also, being more aware of your surroundings gives you a whole new sense of looking at things... like how many exits are in the place you are in... what you could use as a weapon if needed... how people around you are behaving, etc. one of my uncle's best friends was a guy named stephen hayes, and apparently he is some american-ninja-hotshot guy. that's how he learned it.
if i could learn anything, i'd like to give a go at hapkido or krav maga and mix them (with ninpo) all together. but knowing an art and practicing it are two different things.