An act of blasting a hot, silent fart while exiting from a crowded elevator. Ideally, the gas should be leaked just before you exit through the closing elevator door. The remaining riders are trapped in the chamber to enjoy the fully marinated scent.
Variation: The Echo Chamber. Performing a Chamber of Secrets, but substitute a silent secretion with a loud, shreeking fart as you emerge from the elevator.
After eating a foot-long meatball sub from Subway, I performed a chamber of secrets in the hotel elevator, shouting "Jared" as I exited.