A good weapon to learn is kusari fundo or short cord (for safe training). The kusari fundo is a chain around 46 to 76 cm in length and weighted at both ends. It looks so simple lying there. It is easy to transport. And variations on it can be found everywhere in daily life if you don't happen to have the weapon itself.
Most students can immediately put it to use by swinging it through the air with one hand to strike a target with the weighted end. Or shooting a weight out like a dart. Seems simple. But even this simple idea requires some Bujinkan fundamentals of angles, distance, timing. Without these, targeting will be ineffective. And to compound matters, the weapon can backfire on its owner! Anyone who has practiced with Nunchaku will understand this clearly.
After swinging and striking, the next obvious use is grappling. Wrapping and tangling an opponent's arm or sword are common uses. But again, the weapon can trap the user. I've witnessed many people attempting to grapple with the weapon and their own minds are wrapped up in the effort. Their hands grip the chain with white knuckles where they themselves are trapped.
Other uses are striking with the weights or chain alone. Holding a weight in a fist and hammering away can really drive home a shattering blow. Or the chain can make a stinging, whip like attack. Snap the chain from loose to taught and it makes a very useful strike. Sometimes the whole thing is thrown like a projectile weapon to entangle or distract. It can be thrown as one mass, or spun like a helicopter.
If you think you understand the above methods, you might be missing the true beauty of this weapon. As I stated above, flexible weapons are unruly. Difficult to control. And that is their advantage. If you watch Hatsumi Sensei use them he lets them do what is in their nature. He doesn't care if it is messy or full of knots or doesn't look clean. Sometimes the more chaotic, the happier he seems. This is one of the highest lessons for weapons in general. Don't try to be expert with a weapon. Let the nature of the weapon come out. Listen to its secrets. If you try to control it, you will be controlled.
A kusari fundo hint: Play with tension and slack. When you find tension be slack. And tense! Have Yoyuu. As my friend Paul Masse describes:
When you have Yoyuu, you are not in a hurry. You can take your time. Having Yoyuu allows you to have more space, more time, and more freedom in your movement. When you have yoyuu, you can wrap your opponent up in not only technique but with your heart as well.
A weapon is just a tool. Use it. Let it go. Sometimes let it just pass through your hands and your life.