Springtime toy

In this post, I’m soliciting some ideas- we have a lot of fun playing with springs and D knows all her major types already. What I’d like to do is come up with a good demonstrator application. In most cases you can sort out a way to substitute one type for another, but I’d like to come up with a fun assembly that effectively utilizes each type in its most appropriate configuration. Maybe like a fully automatic rubber band gun with a wind up (constant force) trigger, leaf spring ratchet and compression spring return? I dunno- am I even asking this question clearly? Anyway thanks for any ideas!