Here is one I like to pull out once in a while:
I keep a bag of balloons in my locker at work (indoor range).
I'll stuff one inside another, blow up the inner one to about 4-5 inches and tie it off.
Then I'll blow up the outer one to a few inches larger and tie it off.
I'll hang the whole thing downrange about 10 yards. I'll shoot only the outer balloon, then try to pick up the smaller one and hit it before it hits the ground. It kicks out at random angles each time, so while it is an achievable challenge, it isn't easy.