In Angry Birds Friends, you can buy and use assorted slings.
Some are reasonably obvious (Wood increases damage against wood blocks, ditto ice/glass and stone. Gold increases damage against everything. Xmas tree throws ornament shower). And they have descriptions when you select the sling in the shop.
Some special ones, don't have a description, and I don't quite understand what the those slings do. What are the effects of Wishbone (all the store says is, it's spooky Hallowin version of Gold). What effect does bubble one have? (it produced bubbles but they don't seem to have any use?). What does Diamond do?