A theme park simulator ride, completely themed around an airport and getting on a plane. Unlike most simulators, the focus would be on the ride vehicle which is made up to look like the inside of part of a standard passenger jet. The plane could pretend to shake and show turbulence. Onto the windows could be projected what one would see if one was really in peril. You could have the captains voice and flight attendants too, screaming and so forth.

I think this would really play on peoples' fears of flying and would not need to be too intense as long as the theming and realism was up to standard. As I say, this is unlikely to ever be built, especially in the US but would be scarier than any rollercoaster. Perhaps too scary.