The clothing of the true ninja is not black. Popular belief states that it is black, but this would be foolish. Black is a very easily visible color under almost all circumstances. In fact, the ninja's clothing is gray. Gray fades in well in many lighting circumstances, and does not draw attention to itself.
The cloth of the ninja's clothing is a loose, open weave of soft fabric. No stiff, starchy fabrics that impede movement or make noises while worn. Corduroy is right out.
Unlike their cloth, the blades of the ninja must make noise. For dramatic effect, after all. How would you feel if a ninja snuck up on you and killed you with a totally silent sword? You'd feel completely robbed, that's how you would feel. You might not even know you're dead and go on for days until someone asks you how you got your throat sliced like that. Not good.
The true ninja weapon is specially crafted in a way that takes horrendous amounts of time. So long, in fact, that most ninjas die before their weapon is complete. So they usually use "loaners" from ninjas that already died until three generations of craftsmen have finished making their blade (which will get loaned out to future generations of ninja, which is why they don't cancel their sword orders when they find out how long it will take to laboriously beat it out 5000 times, quench it in the blood of enemies 175 times, in the first snow of winter 50 times, and be tested in the traditional ways such as slicing a three foot long hair from a princess falling through the air on the first day of spring (it must be split lengthwise perfectly, or the craftsman is killed, the sword is melted down, and another craftsman starts all over), cutting the kanji for "shadow warrior" into the wings of a fly as it passes overhead (failure results in the same penalties as for the hair), and slicing a lesser sword into several pieces without getting a single nick in the blade (this one is usually a "gimme", as the craftsmen have learned that "lesser sword" can include those made out of cardboard or meatloaf.)
OK, so, the Noise...
The sword also needs to make a really cool "whoosh" or "swish" noise. After all, that's what people expect. You're sitting in your study, making plans to overthrow the dynasty. Suddenly you hear an unexplained "whoosh", and see your bodyguard fall gurgling to the floor. You look for the source of the noise, only to hear "swish!" and see blood running down your front. Now you know that a Silent Warrior has dispatched you properly. No wondering for days if the itch on your throat is a rash or something before you discover that you've been dead for days.
Ninjas don't use those silly throwing stars like they sell in shops for dumb tourists. Their shuriken mean business . They're really a sort of slightly undersized railroad spike. When some bodyguard or nosy householder gets one of these planted in their forehead, they won't be running off going "Owie, owie!" They'll stop whatver they were doing and drop dead.
Ninjas also use rope a lot. After all, they don't have super spider powers. They like their rope like their robes, gray, soft, and supple. They don't use orange polypropylene trash like they sell at your corner sporting goods shop.
When things go sour for the ninja, the true ninja always has an "ace in the hole". It's their tactical nuclear weapon. Most ninjas prefer a yield of from 4 to 6 kilotons, just enough to take out the target and cover the ninja's tracks. The ninja trains long and hard during their apprenticeship to do one of those flipping through the air jumps to escape the force of the blast themselves. In fact, they do not entirely escape the blast, but they use the force of the initial conventional triggering charge to blow themselves clear of the main explosion. So if you're ever walking along and a slightly singed ninja drops out of the clear sunny sky on the sidewalk nearby, it's a pretty good guess that the ninja has had to resort to his "backup". You'll also want to "duck and cover" before the blast gets to you, since you haven't had years of training in atomic ninjitsu.