I got to play a Williams Travel Time recently at the Ottawa Pinball Show. Cool machine where draining can actually be advantageous. This is a game where you play against the clock and not based on # of balls. Time is always counting down but you can add time with certain shots.
Are there any other games like this?
(I was thinking that this would be a cool way to design an RPG style machine with a hit point / damage / healing scheme. Maybe draining in such a scheme causes 'damage' but doesn't kill your ball if you still have hit points left!)