Off the top of my head, here are some things I would like to see:
- Randomizer: a flip gate that redirects the ball randomly
- Column Collector: a container that collects balls in a vertical stack
- Release Trigger: a part that can be placed anywhere on the board which triggers the release of another ball.
- Weight trigger: a collector part that becomes a ramp after a certain number has been collected.
- Hold and Release: a part pair where one part will hold a ball and then release it when the other part anywhere on the board receives and holds a ball.
- Lift: a way to automatically return balls to the top of the board.