Me & the usual suspects I travel with will typically utter something when on a dark ride:
-Tower of Terror ("Let me off!" when the elevator door closes, usually a smart power-outage remark when the video is through playing at the beginning)
-Space Mountain (always snap a photo in the blastoff tunnel and pretend like I'm reaching out to high 5 other riders when we're slowly moving up the track and they're flying down on the opposite side),
-Countless "scared" expressions on Dinosaur
-Drum along with the track in the Buzz Lightyear queue.
I know I'm forgetting a bunch here. I'll just have to post them later when my brain is working properly. Haha.