Good article and link:
Hunting with a Slingshot | ShilohTV
When I was a kid I was deadly with the home made “beanshooter” or “bean-flip”. Our slingshots were home-made from the crotch of a dogwood tree, with natural gum latex ruibber bands or 3/8 sugical tubing bound to the upright forks with #32 rubber bands or 15-lb. braided nylon fishing line, then varnished.
While dried peas and Great Northern beans were common training ammunition for boys below the age of 12, as teenagers were were entrusted with lead buckshot as serious hunting ammunition. It was Dad’s rule that boys could not hunt with a gun unsupervised until old enough to have a “learner’s permit” to drive. But wandering the woods with a "bean shooter" was OK.
A boyhood friend had an original Colt 1851 Navy cap & ball revolver which we learned to shoot under Dad’s supervision, but at other times the .375 round balls we cast in the barn over a Coleman stove became our preferred, hard hitting slingshot ammo to harvest rabbits for stew out of Mom’s flower bed, raccoons attacking garbage cans behind the back porch at night or groundhogs whenever we could “Indian-up” on one along the garden fence or wood line.
Many urban areas restrict the sale of “wrist rocket" slingshots because they are commonly used as “gang weapons.” If you are reduced to making your own, you can do much worse than follow the methods depicted by the famous Bean Shooter Man Rufus Hussey of Ashboro, NC, and reproduce his lowly “Bean Shooter.”
This link has how-to information. This is EXACTLY what I used as a boy. Mine has taken alot of rabbits and game birds and in a pinch it still would be a quiet self defense weapon. To carry a "loaded slingshot" in your overalls back pocket, so that it is available for a fast draw, (with practice as boys we could draw and shoot a pop can at 20 feet in 2 seconds) a single, large projectile, such as a 9/16 ball bearing or glass marble is centered in the leather pouch, which should be very LIGHTLY greased with Crisco, and retained by a rubber band, doubled and tucked snugly around the pouch. When the slingshot is drawn and released, the rubber band discards neatly, sending the marble or ball bearing on its merry way.
http://www.asheboro.com/users/teallen/rufus1.htm 
