Boomerang Rubber Band (Twanging)
This is not a juggling trick, but is popular at juggling conventions that I have been to. I originally heard it called the boomerang rubber band, but more recently I've heard it called "twanging". I don't have a video of the actual trick here because the rubber bands I have are almost exactly the same color as the floor and carpet in my house and it doesn't show up. The trick is to shoot a rubber band, have it land on the floor and roll all the way back to you. It's really cool.
First, get some rubber bands. I use #16 size. If you're just digging through the drawer looking for something, look for a skinny, round one. The diameter of the circle is about 1.75 inches, or about 4.4 centimeters.
Hold your hand with the fingers all spread out, especially the pinkie and thumb. They should be spread as far as possible. I the palm of your hand should be toward you with the index finger pointing upward and the pinkie and thumb out sideways. Put the rubber band over the end of your pinkie finger, underneath the nail, but if you have long nails, don't wedge it under. The other end of the rubber band goes under your thumb nail, but the bottom half of the rubber band should be stretched completely tight. This, of course, makes the top part very loose. Now grab the top part of the rubber band near your thumb and pull toward your pinkie, and down slightly. Your index finger needs to push down at the middle of the rubber band. This should make the rubber band tight on the bottom and tight on the top half nearest your thumb All the loose rubber should be on the top between your index finger and your pinkie. Push down on the middle with your index finger and move your thumb forward so that the rubber band forms an acute angle (about 60 degrees). Hold everything still and pull your thumb out to shoot the rubber band. It should shoot out about 8 or 10 feet, land on the ground and roll back to you.
This took me about an hour to learn. My hand hurt a lot. You will be using some muscles that are not used for anything else that I know of. The rubber band you use needs to be fresh. Old, stretched out rubber bands don't work and new ones are only good for a few shots before they start to get stretched out. At first, you'll probably stretch out some rubber bands just trying to get them on your hand right, so even if you do it right, it's possible that they won't roll back.