[thinker&planner]

One way to make a piston into a possibly better shooting using a "simple machine" would be to attach a piece of chain to a piston and wrap the chain around a curved piece of aluminum which is then attached to a kicker.
I know this is a bad description, but basically, when the piston retracts, it pulls the kicker around a pivot point, creating a "knee" joint and a mechanical leg kicker.