I am going to cheat here, because there's no possible way I can pick one.
Rock n' Roller Coaster for the sheer, pulse-pounding thrill of it. I like going upside down, too. ;-)
My heart just catches whenever I'm on Soarin'. It's so beautiful.
PoTC because it's classic, and it makes me feel - probably more than any other ride - that I'm at Disney.
Splash Mountain, because it's a perfect, immersive experience with a story, music, the biiig drop and bonus, it's a long ride, so more bang for your buck so-to-speak.
Expedition Everest because I rode it in its heyday and it really was just a brilliant, brilliant ride. Without the Yeti, it's still great fun and the backwards bit always makes my stomach flip. Love.