Swing set
When I was a kid, I removed the swings from the swing-set and attached a huge length of elastic I found onto each end of the frame. Voila, a giant slingshot that launched marbles very effectively.

I have no idea how far it actually shot marbles. Over the neighbor's and over the next street. How much further I never found out. I figured horizontal shots at the neighboring houses would be too easy to trace.
(xixax, Mon 1 Aug 2016, 12:27, Reply)