Has to be Space Mountain. Not the fanciest, but the queue and the queue *music* was always so cool and other-worldly, it's fun hearing people hoot and scream all throughout the ride and feeling like you're going to get your head or hands chopped off, it feels cool that you sit alone instead of next to someone, so it's a more personal experience, and it was ALWAYS the first ride we had to run to as kids. I would be so devastated if they did anything to Space Mountain once Tron opens.