The sling is a common and often deadly weapon, but it often was used in conjunction with a leathery "strap" that helped throw the missile, I was wondering, did the Ancients have a slingshot type of weapon (http://en.wikipedia.org/wiki/Slingshot)?
Having a slingshot seems like a more versatile and ubiquitous weapon than a leather strap style that required more skill.
You need something elastic to store the energy, to make a slingshot function. That vulcanized-rubber strap is rather recent. The ancient elastic things would be twisted rope or hair- like the onager. But those both have a lot of internal friction, that takes away a lot of the energy- and also lose a lot of their spring when they get wet.
So, the best elastic possibilities for storing and releasing energy for projectile throwing were bow-like things, of wood, horn, or steel. Gravity, however, seems to have worked the best for this. Gravity would be used in a trebuchet- a lever with a big counterweight on it, or a lever with a bunch of idle soldiers hauling down on it.
Elastic sling shots as we know them now did not exist back then. The type of sling shot that was used "by the ancients" was a strap that would have a spot to put a pebble in it. It would be spun around in a circle until it gathered a lot of energy, at which time the slinger would release one end of the strap causing the pebble to travel in an aimed direction at great force. Such weapons were pretty common from what I have seen well into the height of the Roman Empire. The Greeks were even known for engraving smart-ass remarks into the stones or chunks of lead thrown by the sling.
Here is an illustration of what it looked like and how it was used.
http://www.rapturenotes.com/slingsandstones_files/slingers2.gif
