AirTrain connects JFK airport with Jamaica Station (among others). It's smooth, futuristic, and very convenient. I think SFO's building their own AirTrain, to connect with, well, something, I'm sure. Maybe BART or Caltrain. In any event, JFK's AirTrain was nifty. And, I had both cars in my module completely to myself after we left the airport terminals proper.
The switches were cool looking but my train always kept going straight.
(Click the image to view a smaller version.)