Well I love S:ROS at SFA at night, because beyond the lift, it's pitch black. It was also fun to do the negative-g trick on the third hill with some glow sticks. I also love Chiller at SFGADV at night. Although the ride isn't that good, it is great to see the whole park lighted up when you reach the 200 ft. peak of the Chiller. Medusa also makes for a good night ride, and so does B:TR when they shut the course lights off.
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Parks for 2000: CP, Great Escape, Great Adventure, SFA, Islands of Adventure, Kennywood