Well I think instantly to the designs like
“Ysling” “kestros” “captured release” “compoundsling” “multi pouch” “triggering sling” “shotgun sling”


Personally I’ve played around with a few of these but only a few seemed to have any real appeal.

Here’s a picture of the triggering mechanism I came up with . I was very happy when I came up with the idea for the first time. Simple and very easy to use and reload , but it made ammunition variability almost impossible so it held no true promise for my applications.

I won’t tell exactly how it works see if anyone figures it out.

I had nearly the same reaction as stoneslinging I had no idea how in the world it would work!
After a while looking at it, I showed it to my brother, who came up with a probable way to make it work

The only other really unique sling I can think of is the cestrosphendone / kestrophendone dart sling (http://slinging.org/forum/YaBB.pl?num=1074713443, https://www.youtube.com/watch?v=r5PWq3XqGGw, https://www.youtube.com/watch?v=0mMUOZZBDuY).

Another sling that is at least sort of unique is the staff sling.

Here's my Double Barrel Sling.  As long as you use consistently sized ammo you'll get a pretty tight shot group.  Or you can use both pouches to sling larger objects like snowballs. 

Very interesting Rat Man, never seen a double-action sling before haha