Atlanta!!!

Atlatl. Or simply spear-thrower.

It's a bit like a fing-longer, but for your whole arm, and therefore more useful.

Same principle as the sling: they make your arm longer so the "hand" moves faster when you swing it, allowing you to throw stuff at higher and more lethal speeds, and farther.

We're still quite lethal even without these tools though, just look at baseball pitchers.