Bass. Because Bass run in schools here in Texas in the Summer time. When we see the shad jumping on top of the water, you can bet there are Bass under them - so we throw any thing that resembles a wounded shad. The bigger bass are usually deeper so with the clattering double spoon it is heavy enough to get down to them quick.
Although I'm sure it would be good on Lake trout or pike. Some of you guys up north ought to try this. Let me know how it works out.