Originally posted by Joel Stave
something called a "wrist rocket" that looked exactly like the picture you posted.
"Wrist rocket" is the more proper terminology - though it comes from a name-brand (much like "kleenex") - for the picture above.
A sling shot is typically without the wrist brace.
My favorite was a folding version of the wrist-rocket.
By the way, if you are ever out of pebbles, marbles, steel balls, etc. you can always use dog food (provided the pieces are round). I'm not sure how successful a "kill" you could get, but we had plenty fun knocking over bottles, busting light bulbs, and were able to hit with decent accuracy on homemade paper targets from 25 ft.
I once got hit by a dog food pellete from about 75 ft. away (courtesy my younger brother). Boy did that hurt. Right on the knuckle of my left hand - ouch!
The coolest part of the dog food ammo was that if the target was hard enough, the pellet would explode in a cloud of brownish dust.
Dan
[edited to add]
Oops! forgot to add that I once carved a slingshot out of a crook in a tree while down in Guatemala. It was a nice hard wood and I carved finger notches into to fit my hand perfectly. I made straps from scrap rubber cords (real rubber - nasty stuff). Then lashed it to the ends with some leather strips. The strips as well as the pouch came from an old boot. The toe lent itself nicely as the pouch and I found that I could shoot just about any shape rock at least 50 yds. I mostly used it to hassle squirrels (who were also hassling me) and for target practice. I never scored a "kill", but then again I wasn't "hunting" either.